In aviation, the flight length is defined as the time airborne during a flight. There are four categories, short-haul, medium-haul, long-haul and ultra long-haul.

Distinctions

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.