Flight planning

Flight planning is the process of producing a flight plan to describe a proposed aircraft flight. It involves two safety-critical aspects: fuel calculation, to ensure that the aircraft can safely reach the destination, and compliance with air traffic control requirements, to minimise the risk of midair collision. In addition, flight planners normally wish to minimise flight cost through the appropriate choice of route, height, and speed, and by loading the minimum necessary fuel on board. ATS use the completed flight plan for separation of ACFT in ATM services, including tracking and finding lost ACFT, during Search and rescue(SAR) missions.

Flight planning requires accurate weather forecasts so that fuel consumption calculations can account for the fuel consumption effects of head or tail winds and air temperature. Safety regulations require aircraft to carry fuel beyond the minimum needed to fly from origin to destination, allowing for unforeseen circumstances or for diversion to another airport if the planned destination becomes unavailable. Furthermore, under the supervision of air traffic control, aircraft flying in controlled airspace must follow predetermined routes known as airways, even if such routes are not as economical as a more direct flight. Within these airways, aircraft must maintain flight levels, specified altitudes usually separated vertically by 1000 or 2000 feet (305 or 610 m), depending on the route being flown and the direction of travel. When aircraft with only two engines are flying long distances across oceans, deserts, or other areas with no airports, they have to satisfy additional ETOPS safety rules to ensure they can reach some emergency airport if one engine fails.

Producing an accurate optimised flight plan requires millions of calculations, so commercial flight planning systems make extensive use of computers (an approximate unoptimised flight plan can be done by hand in an hour or so, but more allowance must be made for unforeseen circumstances). When computer flight planning replaced manual flight planning for eastbound flights across the North Atlantic, the average fuel consumption was reduced by about 1,000 pounds per flight, and the average flight times were reduced by about 5 minutes per flight. Some commercial airlines have their own internal flight planning system, while others employ the services of external planners.

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