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In aviation, the flight length is defined as the time airborne during a flight. This definition is independent of absolute distance covered, although the categorization as short, medium, or long-haul can be affected by whether the flight is domestic or international.
|Short-haul flight:||<3 hours (International)|
|Medium-haul flight:||3 to 6 hours|
|Long-haul flight:||6 to 12 hours|
|Ultra long-haul flight:||>12 hours|
- Absolute distance versus flight length
A flight is typically planned to follow a direct route wherever possible to minimise flight length. For long-haul flights, the most direct route follows a great circle along the diameter of the earth. For example, aircraft travelling westward between continents in the northern hemisphere often follow paths extending northward near or into the arctic region. When shown on a conventional projection of a world map, the resulting route looks curved and appears longer than it really is. The great-circle distance between airports may therefore give a better indication of the shortest flight length.
However, a flight route must also take into account weather conditions, air currents, and fuel economy. A long-haul flight in an easterly direction often takes a longer more southerly route than the great circle in order to take advantage of the jet stream, a high-altitude wind that can allow an aircraft to cover a longer absolute distance using less fuel than on a more direct route.
- Air time versus time zones on the ground
Time on the ground will be affected by time zones. So a pilot flying westwards, or "chasing the sun", lengthens her day, and conversely an eastbound flight is shortened in terms of clock time. This does not affect the classification as long, medium, or short haul.
- Short-haul flights
Airline definitions differ on what is to be considered a short-haul. A short-haul domestic flight (where the destination airport is in the same country as the departure airport) is commonly categorized as having a flight length taking under one and a half hours to complete. This roughly correlates to an absolute distance of no more than 500 mi (800 km). By this definition, all domestic flights within relatively small countries like the United Kingdom are short-haul.
An international short-haul flight is typically longer. Thomas Cook Airlines defines it as a flight taking less than three hours to complete. A short-haul flight for Cathay Pacific may be a flight between Hong Kong and Taipei or Manila. For Etihad, a short-haul might include a flight from the UAE to India. In the United Kingdom, Air Passenger Duty is levied on all flights by the UK Treasury according to banding by distance. It defines a short-haul flight as an absolute flight distance under 2000 miles.
- Medium-haul flights
On international routes, a medium-haul flight lasts from three and six hours, for example between the United Kingdom and Egypt, which requires approximately five and a half hours to complete. Like long-haul flights, medium-haul routes can be domestic in larger countries; flights between the east and west coasts of the United States also average around five and a half hours.  In smaller countries, a medium-haul flight is often defined as having a flight length that takes one and a half hours or more to complete, which roughly correlates to an absolute distance over 500 mi (800 km).
- Long-haul flights
A long-haul flight is typically made by a wide-body aircraft, such as Boeing 767, Boeing 777, Boeing 787, McDonnell Douglas DC-10, Airbus A330, Airbus A340, Airbus A380 or Boeing 747. The flight length typically requires over six and a half hours to cover and is often a non-stop flight. Only a few narrow-body aircraft, such as the Boeing 757, have true long-haul capability. These aircraft are commonly used on secondary transatlantic routes.
- Ultra long-haul flights
An ultra long-haul flight is typically made by a long-range wide-body aircraft such as the Boeing 777-200LR, the Airbus A380-800 or the Airbus A340-500, such as Dubai to Toronto and Dubai to Los Angeles by Emirates with its Airbus A380-800. These flights involve the longest distances flown by commercial aircraft, requiring over 12 hours to cover, and are also often non-stop flights. The longest such flight, Qantas flight 8 from Dallas to Sydney (DFW-SYD) is also an Airbus A380-800, The previous longest non-stop flight Singapore Airlines Flight 21 from Newark to Singapore, covered 9,534 miles (15,343 km) in about 18.5 hours flight time used an Airbus A340-500 
Lufthansa Regional CityLine Avro RJ85, a typical short-haul aircraft
Boeing 737-700, a typical medium-haul aircraft
- List of short-haul civilian aircraft post war
- List of short-haul regional airliners
- List of short-haul narrow-body airliners
- List of ultra long-haul civilian aircraft post war
- Regional airliner
- Wide-body aircraft
- Non-stop flight
- Flight distance record
- International flight
- Dik A. Daso Doolittle: Aerospace Visionary 2003 - Page 116 "While flying west, a pilot actually lengthens her day by “chasing the sun.” Hence, there are effectively three hours more daylight than darkness on this east-to-west flight. "
- Eaves, Matthew (2008). How to Survive a Long Haul Flight. London: Mandival. ISBN 978-0-9559844-0-2.
- Thomas Cook Airlines - Prices
- "Singapore Air makes longest flight". CNN. 2004-06-29.[dead link]