JP6248104B2 - Schedule management system and method for managing air traffic - Google Patents

Description

  The present invention relates generally to methods and systems for managing air traffic. In particular, the present invention relates to a method and system used to optimize air traffic control operations and minimize loss of air traffic efficiency resulting from the delay of one or more aircraft to a scheduled arrival time (STA). Included are methods and systems for managing time schedules of arriving aircraft by including early cruise drops as a means of absorbing time delays.

  Managing the time schedule of aircraft approaching the arrival airport is an important air traffic management task performed by air traffic control. Despite weather effects and other air traffic disturbances, it is important to deliver arriving aircraft to an arrival meter measurement point within the STA's acceptable parameter range. In modern air traffic, a single plane lagging behind the STA will probably result in downstream air traffic, including losing slots.

  An accurate four-dimensional flight path (4DT) in space (latitude, longitude, altitude) and time allows air traffic control to assess the future location of air traffic and aircraft. These parameters can also be used by air traffic control for schedule management purposes, absorbing air traffic delays, longitudinal (speed change), lateral (extension or shortening of the flight path), or vertical ( The arrival time of downstream air traffic can be changed by changing the cruising altitude to reduce speed). Currently, a combination of speed change and flight path lateral change is used to absorb the time delay.

  As used herein, a flight path is a time-ordered sequence of three-dimensional positions that an aircraft follows from takeoff to landing and can be described mathematically. In contrast, a flight plan is a set of documents submitted by civil aviation pilots or flight managers, including information such as departure and arrival locations and times, and tracked by air traffic control (ATC). And can be used to provide routing services. The flight path is uncertain about time and position, but is a means of achieving the intended flight plan.

  Flight-based operation (TBO) is an important component of the advanced air traffic system that will be realized in the near future, the next generation air transport system in the United States (NextGen) and the single unit in Europe. Includes Single European Sky ATM Research (SESAR). The TBO concept provides the basis for improving airspace operational efficiency. Flight path synchronization and negotiation performed in TBO allows airspace users (including flight operators, flight managers, flight deck personnel, unmanned aerial systems, and military users) to get closer to their preferred flight path. It allows you to fly regularly and allows management objectives to be incorporated into the TBO concept, including fuel and time efficiency, optimal routing to wind, and weather related flight path changes. As a result, significant research is being conducted in the development of system frameworks and technologies to enable TBO.

  The goal for all of TBO is to reduce the uncertainty associated with the prediction of the future position of the aircraft by using the above-mentioned 4DT in space and time. The precise use of 4DT drastically reduces the uncertainty in determining the aircraft's current and future position and flight path over time, and when the aircraft approaches its arrival airport, when the aircraft is Including the ability to predict whether to reach a fixed point, a fixed point of arrival, or a geographical location, also called a corner post. At present, air traffic control relies on a "control based on control approval" system, which usually relies on observation of the aircraft's current location without much knowledge of the aircraft's flight path. Usually this results in the aircraft flying on a route that is determined by air traffic control but not the preferred flight path of the aircraft. By switching to TBO, the aircraft can fly a flight path suitable for the user.

  In TBO, user preferences determine the choices made in air traffic operations. More specifically, aircraft flight paths and operational procedures are a direct result of aircraft operator management objectives. The basic element of these management objectives is the cost index (CI), which is the ratio of the cost of time (cost per minute) to the fuel cost (cost per kg) of the aircraft in flight. An aircraft's CI determines its optimal flight speed and flight path, and is a function of atmospheric conditions, aircraft performance, and flight path, so that it is almost unique from flight to flight. Furthermore, factors such as speed and altitude do not necessarily increase linearly with increasing CI. Thus, CI calculation in ground simulation is difficult.

  At present, air traffic controllers maintain route patterns primarily considering safety and separation between aircraft. Such a pattern is created without considering a preferred aircraft flight path, so the air traffic controller makes no effort to save the cost of the aircraft operator. In such cases, it is recognized that other possible flight path changes can be made that are much more cost effective. The optimizations and calculations necessary to determine a suitable flight path are probably not possible with a human operator or controller and will need to be provided by a computer system. In such a case, the computer provides suitable flight path options for the human operator, and then the operator selects from a series of possible flight paths.

  In order for TBO to function efficiently, it is necessary to accumulate and compile flight path data from all relevant aircraft. The user-friendly flight path, i.e. the flight path most desirable by the aircraft operator, can often compete with each other, especially in air traffic systems that are no longer based on control approval. TBO improves efficiency, but it must deal with flight paths and traffic contention. Flight path negotiation determines the flight path requirements or intentions of various aircraft and attempts to make the best use of available airspace by creating a solution that satisfies as many user preferences as possible. Such flight path negotiation relies on aircraft flight path data, as well as human decision making and flight path selection.

  Currently, similar to speed changes, lateral changes to the flight path are used to absorb flight delays in air traffic. However, it would be desirable if the early descent flight path could be used to absorb air traffic flight delays. NASA's Ames Research Center works with NASA's Channel Descent Advisor (EDA) by performing simulation experiments with humans in a loop with experienced air traffic control center (ARTCC) district controllers. The feasibility of using the altitude change (descent) advisory capability was investigated. This was published in the AAAA Guidance, Navigation, and Control Conference (August 11-11, 2011 in Portland, Oreg., USA) “Impacts on Intermediate Cruise-Critical Conflict-Frequency Conflict— It has been reported.

  In a continuous descent or early descent flight path, the aircraft begins to descend at an idle or near idle thrust setting much faster than the standard flight path. By initiating a slow descent fairly early in the flight path, time delays can be absorbed and fuel consumption can be reduced. A basic schematic of the early descent flight path is shown in FIG. An aircraft that follows an early descent flight path may descend continuously to a designated metering point location, or it may descend to an intermediate low altitude, absorbing flight delays and potentially fueling You can fly at lower speeds to consume less.

  If air traffic time delays must be absorbed, early descent operations can provide a clear cost advantage over lateral or speed changes to the flight path of the aircraft. However, especially when human controllers are concerned about preventing air traffic competition, meet air traffic safety constraints to absorb appropriate delays and save fuel Determining a suitable flight path would go beyond the computational capabilities of a human controller. Accordingly, preferred flight paths or several suitable flight paths that can include an early descent operation can be determined and these flight paths can be routed to a human controller that can communicate commands to the aircraft pilot. A system that can be provided must be realized. In the event that air traffic competition requires aircraft operation to absorb the time delay, the system will continue to be aware of air traffic safety and operational constraints by surrounding traffic, Provides flight path options suitable for simple horizontal or vertical changes.

  U.S. Patent Application Publication No. 2009/0157288 attempts to solve a similar problem, but limits the subject of the solution to individual aircraft. The aircraft receives only the time delay factor from air traffic control and is isolated from additional information from the ground system to determine the best flight path change to address this time delay.

  While information and decision making can be left entirely in either an aircraft or ground system, either of these methods has limitations on the accuracy and availability of the information. Normally, such calculations depend on the overall air traffic situation near the aircraft, and therefore the results of such decisions are not separated for the aircraft.

US Patent Application Publication No. 2010/241345

  The present invention provides a method and system for managing the time schedule of arriving aircraft approaching an arriving airport. The present invention includes, but is not limited to, early cruise descent to compensate for air traffic scheduling changes including, but not limited to, time delays resulting from one or more aircraft lagging behind the STA (scheduled arrival time). Provide a means to change the aircraft flight path that is not.

  According to a first aspect of the present invention, there is provided a schedule management system for managing air traffic including a plurality of aircraft that are in a defined airspace and approaching an arrival airport. Each has existing flight path parameters including 3D position and velocity. The schedule management system is an airborne flight management system (FMS) individually associated with a plurality of aircraft and adapted to determine cost data specific to the aircraft flight path and aircraft flight associated with the aircraft flight path; An air traffic control system adapted to monitor a plurality of aircraft, but not installed on any of the plurality of aircraft. The air traffic control system has a decision support tool, obtains aircraft flight path and flight-specific cost data from the FMS, and has multiple data for at least one position (eg, measurement points) along the approach path to the arrival airport. Operable to generate a STA for each of the aircraft. Any of the plurality of aircraft is delayed at that location to that STA, thereby delaying the second aircraft to impose a slower STA on the second aircraft of the plurality of aircraft flying toward that location In this case, the air traffic control system sends the aircraft flight path and flight-specific cost data to the decision support tool, and special flight path changes are made to absorb delays associated with slower STAs. Operates to send instructions to the second aircraft based on human decisions facilitated by the decision support tool, using a decision support tool to determine whether it is more economical for the second aircraft Is possible.

  According to a second aspect of the present invention, there is provided a method for managing air traffic including a plurality of aircraft within a defined airspace and approaching an arrival airport, each of the plurality of aircraft Has existing flight path parameters including 3D position and velocity. The method includes determining aircraft flight path and flight-specific cost data for each of a plurality of aircraft having an onboard FMS associated with the plurality of aircraft individually, and air traffic not mounted on any of the plurality of aircraft. Monitoring a plurality of aircraft using a control system, and generating an STA for each of the plurality of aircraft for at least one location (eg, a measuring point) along the approach path to the arrival airport using the air traffic control system Including the steps of: Any of the plurality of aircraft is delayed at that location to that STA, thereby delaying the second aircraft to impose a slower STA on the second aircraft of the plurality of aircraft flying toward that location If so, the method transmits aircraft flight path and flight-specific cost data obtained from the FMS to the decision support tool of the air traffic control system and absorbs delays associated with slower STAs. To use a decision support tool to determine whether a special flight path change is more economical for the second aircraft, and based on human decisions facilitated by the decision support tool, Sending instructions to the second aircraft.

  While conventional methods of managing time schedules for arriving aircraft rely on information and decision making left entirely on either individual aircraft or ground systems, the present invention is provided on the ground Use aircraft and flight data received from aircraft within the sphere of influence of an air traffic control system (eg, air traffic control center) to calculate the estimated arrival time (ETA) for each aircraft being managed to absorb time delays The present invention seeks to provide an accurate and comprehensive schedule management system that uses a ground system decision support tool (DST) to determine whether an aircraft needs to be temporarily accelerated or not. This is a technical effect.

  Other aspects and advantages of this invention will be better appreciated from the following detailed description.

It is a figure which shows typically the basic schematic of the early descent flight path | route which can be implemented by embodiment of this invention. 1 is a block diagram of a schedule management method and system for managing air traffic approaching an arriving airport based on individual aircraft flight paths and flight specific cost data. FIG. 6 is a graph showing the relationship between a given time delay and altitude change that can be used to absorb the time delay from a specific distance to a metering point in an early descent operation. Compared to conventional lateral or speed changes, potential cost advantages can be achieved when early descent operations are introduced into the aircraft flight path to absorb time delays in air traffic It is a figure showing this.

  The present invention provides a schedule management system and method for managing air traffic approaching an arrival airport. In accordance with a preferred aspect of the present invention, aircraft in the airspace are equipped with airborne flight management systems (FMS) that determine aircraft flight paths and cost data specific to the flight of the individual aircraft on which they are mounted. . The schedule management system receives aircraft flight paths and flight-specific cost data from the FMS of aircraft within the territory of an air traffic control (ATC) center where the ground system is equipped with a decision support tool (DST). The air traffic control system determines the scheduled arrival time (STA) of the aircraft at one or more metering points along one or more approach routes to the arrival airport, whereby the aircraft is delayed to that STA, thereby When imposing a time delay on one or more other aircraft that are flying towards the metering point, the DST determines whether an aircraft flight path change is advantageous in absorbing the time delay. Use aircraft flight paths and flight-specific cost data for other (delayed) aircraft. Where appropriate, such a determination can be sent to the delayed aircraft by the air traffic control personnel.

  According to a preferred aspect of the present invention, flight specific cost information is generated by the aircraft and provided to the DST for analysis. Based on the capabilities of existing computers, the DST is preferably part of a computer system installed on the ground and not onboard an aircraft. If the DST is a much larger size and can be designed to fit into a room or building rather than an aircraft cabin, this provides greater data storage and processing capabilities. A DST installed on the ground also provides a better medium for compiling data received from multiple aircraft under the control of an air traffic control system. Ability of embodiments of the present invention to facilitate advances in air traffic control, especially to accommodate advanced air traffic systems, such as future-based flight path based operations (TBO), including NextGen and SESAR advancements It is necessary to keep in mind that it provides Thus, DST is designed to work with many different aircraft, flight paths, locations, and time constraints, rather than working with just one aircraft.

  An arrival manager (AMAN) is commonly used in congested airspace to calculate the arrival schedule of aircraft at a particular airport. The schedule management system computer system can use aircraft monitoring data and / or predicted flight paths from the aircraft to build a schedule of aircraft arriving at a point that is a metered measurement point, typically at the terminal airspace boundary. Today, this function is performed by the FAA's Traffic Management Advisor (TMA) in the United States, while other AMANs are used internationally. In general, the present invention can use an arrival scheduler tool that monitors an aircraft based on aircraft data and calculates the order and STA of aircraft arriving at a total measurement point. Most current schedulers use a first-come-first-served algorithm to calculate STAs, but there are many different alternative scheduling means, including types of schedules in which a well-equipped one is preferred. DST, on the other hand, accurately executes an early descent flight path (resulting in reduced speed) that delivers the aircraft to a measurement point according to a delay STA calculated by the computer system for the later arriving aircraft. An advisory tool used to generate alternative flight paths that allow

  As a non-limiting example of the implementation and operation of the schedule management system of the present invention, FIG. 2 represents an air traffic conflict occurring near an airport, where two aircraft simultaneously reach the airport's field path. In the scenario described with respect to FIG. 2, one aircraft (shown in FIG. 2) must be delayed so that the other aircraft (not shown) can first enter the field path. Sufficient space is provided between the aircraft. The air traffic controller can simply request that the delayed aircraft reduce its cruise speed or make another simple flight path change, which is most cost-effective for the aircraft operator. It may not be expensive or it may not be a desirable solution. Within the schedule management system, the aircraft was installed on the ground to monitor each aircraft's 4D (altitude, lateral route, and time) flight path (4DT) as it enters the airspace monitored by the air traffic control system. A computer system is provided for the air traffic control system. An aircraft suitably equipped with an onboard FMS (or data communication (DataComm) system, for example) can provide this information directly to the computer system. In particular, many altitude FMS can accurately calculate 4DT data, which can be CPDLC, ADS-C, or another data communication mechanism between the aircraft and the air traffic control system, or flight operations. Another digital exchange from the administrator can be used to exchange with the computer system.

  For each aircraft in the monitored airspace, a computer system associated with the air traffic control system calculates an estimated arrival time (ETA) for at least one metering point associated with the arrival (destination) airport shared by the aircraft. . The ETAs for multiple aircraft are stored in a queue that is part of a data storage unit that can be accessed by the computer system and its DST. In the scenario described with respect to FIG. 2, where the first aircraft (not shown) enters the circuit path first, resulting in the delay of another aircraft (shown in FIG. 2), the computer system is estimated from the aircraft. Based on the information to be transmitted or downlinked, a calculation is performed to determine an ETA for the first aircraft and an appropriate delay time for the delayed aircraft.

  Using 4DT, flight-specific cost data, and selection based on the aircraft operator's management objectives, optionally obtained from the delayed aircraft, the delayed aircraft is also saved while also saving aircraft operating costs by potentially initiating an early descent. The computer system uses DST to calculate some possible alternative flight paths that will appropriately delay and resolve traffic conflicts. In this case, by using an appropriate ATCo interface (eg graphic / user interface), the air traffic controller selects one of the possible flight paths, potentially including early descent, as recommended by the DST. This request can then be communicated to the delayed aircraft. In this way, humans can still make decisions to change the flight path of the aircraft, but calculate and recommend a more cost-effective solution that can include one or more early descent flight paths DST facilitates better operational efficiency. Once the descent flight path request is noted by the delayed aircraft (“Pilot Check”) and implemented (“4DT”), the Air Traffic Control System will continue to monitor the aircraft's flight path to meet the request. Can do. If necessary and possible, the air traffic control system can update the ETA for each aircraft's metering points stored in the data storage queue.

  As shown in FIG. 2, the schedule management system can be implemented to work with respect to the initial and final scheduling horizon. The initial scheduling horizon is the spatial horizon where each aircraft enters a given airspace, for example, an airspace within about 200 nautical miles (370.4 km) of the arrival airport. Once the aircraft enters the initial scheduling horizon, the ATM system starts by monitoring the position of the aircraft. The final scheduling horizon (also called the STA freeze horizon) is defined by a specific arrival time meter point. The STA freeze horizon can be defined as the total measuring point ETA for aircraft in the future 20 minutes or less. Once the aircraft enters the STA freeze horizon, the STA is not changed and the management system is started and timed to execute one of the alternative flight paths devised by the schedule management system DST. Operations are uplinked to the aircraft.

  A basic schematic of a delayed aircraft early descent flight path is schematically illustrated in FIG. 1, where the aircraft begins to descent much earlier than a standard flight path (eg, with a thrust setting near idle or idle). Is specified. By initiating a slow descent fairly early in the flight path, the time delay is absorbed, and in the preferred embodiment, less fuel is consumed. The aircraft may descend continuously to a designated metering point location, or it may descend to an intermediate low altitude, slower to absorb flight delays and consume less fuel. You can fly at.

  The type of early descent maneuvering shown in FIG. 1 and enabled by the schedule management system of FIG. 2 when air traffic time delays must be absorbed clearly exceeds lateral or speed changes to the flight path of the aircraft. Cost advantage can be provided. Experimental evaluations leading to the present invention include simulations of multiple Boeing 737 aircraft types, wind profiles, and timed targets, and the time delay data shown in the graph of FIG. 3 as well as the predicted fuel cost plotted in FIG. Includes simulation to generate. The graph of FIG. 3 shows the relationship between the altitude change necessary to absorb a given time delay and the distance from the total measurement point in the early descent operation. Early cruise descent generally uses more fuel than if the corresponding route extends under constant wind conditions, but the presence of a non-constant wind speed field is compared to when the route extends at a higher altitude. Has been found to potentially provide significant fuel savings. A cost factor based framework has also been developed that can support ground-based calculations for schedule management operations that are timed optimally. A discussion of this type of framework is discussed in Torres et al. In “Trajection Management Development by User Preferences”, 30th Digital Avionics Systems Conference (October 16-20, 2011). Which is incorporated herein by reference.

  The cost of operating a flight can be broken down into fuel costs and other direct and time-related costs, which include crew wages, aircraft maintenance, passenger and cargo logistics, and reduced equipment value Is included, but is not limited thereto. The preferred embodiment of the present invention includes extracting the effective operating cost from the FMS onboard the aircraft. A suitable mechanism for calculating and evaluating operational costs can include the cost index described above and in the Torres article. Such calculations and evaluations for a particular aircraft are probably the aircraft itself, because the hardware requirements needed for data storage and processing are much less than those required for DST for ground-based systems. Is provided. The information processed depends on or directly on a particular aircraft as opposed to being generally related to all aircraft in the air traffic being monitored by a given air traffic control center. Involved. The mechanism then makes that information available (downlink) to the air traffic control system and its DST.

  As mentioned above, the Torres paper includes a discussion of a framework based on cost factors that can support ground-based calculations of schedule management operations that are timed optimally, thereby reducing aircraft costs. A new STA with optimized can be determined in response to the previous aircraft behind the STA. In general, such frameworks are cost-effective for various types of changes in their current planned flight path (currently in terms of speed, lateral path change (increase in path length) or cruise altitude. For the aircraft to calculate (for a planned flight path or absolute cost). In order to reduce the speed, a change in cruise altitude is likely to reduce the cruise altitude, but for example, higher altitudes and stronger headwinds would result in the aircraft required by the earlier aircraft lagging behind the STA. It may be appropriate to potentially increase the cruise altitude if it causes an overall time delay that can be matched to a slower STA. This cost information is sent to the DST on the ground (potentially as a set of cost factors from the aircraft).

  In view of the above, cost information can be used to determine whether a particular course change is a more efficient way to meet a time schedule than, for example, route stretching or another operation. A non-limiting example of such a course change is an early descent flight path that is best suited to an aircraft's new STA, a slower STA that a special example was required by a previous aircraft that was late for the STA. It is. The DST compiles the available information provided by the aircraft to a more useful tool. If a portion of the TBO was described earlier, the DST generates and compiles information that can be used to negotiate flight paths, and the DST preferably uses the information to identify some possible alternative flight paths. One or more of them may be selected by an aircraft operator and / or adapted to existing air traffic environment constraints. Its intent is to make it available to one or more users, not just the preferred flight path, through an appropriate interface that allows the user to make decisions based on the flight path and potential additional information By providing accurate flight data, DST can facilitate better use of the airspace and meet flight paths suitable for aircraft users.

  Accessing the managed aircraft STA, the DST may calculate the aircraft ETA based on the predicted aircraft flight path. If the aircraft's ETA is earlier than its STA, the time delay needs to be absorbed. Conversely, if an aircraft's ETA is slower than its STA, the aircraft needs to be advanced in time. A DST installed on the ground is capable of various combinations of speed changes (as a single speed command, or as a time constraint, such as request arrival time (RTA)), lateral path extension or shortcut, and / or altitude change. Can be considered. The cost surface constructed from the downlink cost factor evaluates the operation to time the aircraft and, more preferably, the time to meet the STA at the arrival meter measurement point and to the best time that appears most advantageous to the aircraft. Used to select.

  In view of the above, the present invention allows early cruise descent as part of the possible options set available for air traffic controllers and extends the options set for timed schedule management. This increases the degree of freedom available over speed changes and path stretches and allows better identification of contention-free flight paths that meet timing requirements in congested airspace. With the means to calculate the wider options set and the costs associated with each option, the business objectives of the aircraft can be considered and satisfied.

  Although the invention has been described with reference to specific embodiments, it will be apparent to those skilled in the art that other formats may be employed. Accordingly, it should be understood that the invention is not limited to the specific embodiments described herein. Accordingly, the scope of the invention is limited only by the following claims.

Claims (11)

A schedule management system for managing air traffic including a plurality of aircraft in a defined airspace and approaching an arrival airport,
Each of the plurality of aircraft has existing flight path parameters including three-dimensional position and velocity;
The schedule management system includes:
An airborne flight management system individually associated with the plurality of aircraft and adapted to determine aircraft flight paths and cost data specific to the flight of the aircraft associated with the aircraft flight paths;
An air traffic control system adapted to monitor the plurality of aircraft, but not mounted on any of the plurality of aircraft,
The air traffic control system has a decision support tool,
The air traffic control system obtains the aircraft flight path and the flight-specific cost data from the flight management system, and for each of the plurality of aircraft for at least one location along the approach path to the arrival airport. Operable to generate a scheduled arrival time (STA);
Any one of the plurality of aircraft is behind the STA of any one of the plurality of aircraft at the at least one location, thereby causing the first of the plurality of aircraft flying toward the at least one location. When delaying the second aircraft to impose a slower STA on two aircraft, the air traffic control system sends the aircraft flight path and cost data specific to the flight to the decision support tool And using the decision support tool to determine whether a special flight path change is more economical for the second aircraft to absorb the delay associated with the slower STA, A schedule operable to send instructions to the second aircraft based on a human decision facilitated by a decision support tool; Lumpur management systems.   The schedule management system of claim 1, wherein the flight-specific cost data includes a flight-specific cost related to at least one time. The special flight path changes, including cruising altitude changes to decrease the speed of the second aircraft, schedule management system according to claim 1 or 2. The special flight path changes, including early descent flight path for reducing the speed of the second aircraft, schedule management system according to any one of claims 1 to 3. Wherein at least one position is a measurement fixed point, schedule management system according to any one of claims 1 to 4. A schedule management system method for managing air traffic including a plurality of aircraft in a defined airspace and approaching an arrival airport, comprising:
Each of the plurality of aircraft has existing flight path parameters including three-dimensional position and velocity;
The method
A computer determining aircraft flight path and flight-specific cost data for each of the plurality of aircraft having an airborne flight management system individually associated with the plurality of aircraft;
A computer monitoring the plurality of aircraft using an air traffic control system not mounted on any of the plurality of aircraft;
A step of using said air traffic control system, at least one of said plurality of aircraft each computer ETA (STA) of the position along the access road to the destination airport are produced,
Any one of the plurality of aircraft is behind the STA of any one of the plurality of aircraft at the at least one location, thereby causing the first of the plurality of aircraft flying toward the at least one location. When the second aircraft is delayed in order to impose a slower STA on the second aircraft, the aircraft flight path obtained from the flight management system and cost data specific to the flight are obtained from the intention of the air traffic control system. The computer sends to the decision support tool;
In order to absorb the delay associated with slow STA than said, and the step of using a special computer the decision support tool in order to determine the flight path change is whether more economical one for the second aircraft,
The decision support based on a determination of human being is facilitated by the tool, the method comprising the steps of a command computer sends to the second aircraft.   The method of claim 6, wherein the flight-specific cost data includes a flight-specific cost related to at least one time. 8. A method according to claim 6 or 7 , wherein the special flight path change comprises a cruise altitude change that reduces the speed of the second aircraft. 9. A method according to any of claims 6 to 8, wherein the special flight path change comprises an early descent flight path which reduces the speed of the second aircraft. 10. A method according to any one of claims 6 to 9, wherein the at least one position is a total measurement point. 11. A schedule management system comprising means for performing the steps of the method according to any of claims 6-10 .