In aviation, the flight length refers to the distance of a flight. When it comes to the generic length factors of a flight it includes the speed, distance & stops of a flight. Commercial flights are often categorized into long-, medium- or short-haul by commercial airlines based on flight length, although there is no international standard definition and many airlines use air time or geographic boundaries instead. David W. Wragg define short-haul routes as being shorter than 600–800 nmi (1,100–1,500 km), long-haul as being longer than 2,200–2,600 nmi (4,100–4,800 km), and medium-haul as being in-between.

The related term flight duration is defined as to the amount of time a single flight (segment) is scheduled to take from pushing back at the departure gate to arriving at its destination gate. It is formally defined by ICAO (International Civil Aviation Organization) as "The total time from the moment an aeroplane first moves for the purpose of taking off until the moment it finally comes to rest at the end of the flight" called flight time, also referred to colloquially as "chocks to chocks" time.

Flight duration is formally measured in hours & minutes as it is irrespective of geographic distance traveled. A route's flight duration can be affected by many things such as anticipated routings, weather, traffic, or taxiing times. Scheduled durations for the same route and airline can also vary on what aircraft is used.

A flight's duration can also be described using the aviation term of "Flight Haul Type", such as "Short Haul" or "Long Haul" that have multiple different definitions depending on originating sources. See the below table for some more prominent examples: