A flight plan is an aviation term defined by the International Civil Aviation Organization (ICAO) as:
Specified information provided to air traffic services units, relative to an intended flight or portion of a flight of an aircraft.14
A flight plan is prepared on the ground and specified in three different manners: as a document carried by the flight crew, as a digital document to be uploaded into the Flight Management System (FMS), and as a summary plan provided to the Air Transit Services (ATS). It gives information on route, flight levels, speeds, times, and fuel for various flight segments, alternative airports, and other relevant data for the flight, so that the aircraft properly receives support from ATS in order to execute safe operations. Two safety critical aspects must be fulfilled: fuel calculation, to ensure that the aircraft can safely reach the destination, and compliance with Air Traffic Control (ATC) requirements, to minimize the risk of collision.
Flight planning is the process of producing a flight plan to describe a proposed aircraft flight. 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. Furthermore, due to ATC supervision requirements, aircraft flying in controlled airspace must follow predetermined routes.
An effective flight plan can reduce fuel costs, time-based costs, overflight costs, and lost revenue from payload that can not be carried, simply by efficiently modifying the route and altitudes, speeds, or the amount of departure fuel.
From the point of view of ATS provision, the flight planning process starts when the company declares its intention in operating a particular route and finishes when the aircraft takes off. The importance of planning can be seen from two different perspectives: on the one hand, airlines have to assign its (limited) resources; on the other ANSPs need to know the demand in advance and adjust its capacity to it (if impossible, to modify the demand).
The process to follow has there main milestones:
- Coordination of slots.
- Presentation of the flight plan.
- Assignation of departure time.
14. ICAO Document 4444.