Sortie

Sortie is a term for deployment or dispatch of one military unit, be it of aircraft, ship or, in older times, of columns of troops from a fort. The unit usually has a purpose of accomplishing a specific mission, whether alone or with other aircraft or vessels.

Siege warfare

In siege warfare, a sortie, or sudden issuing of troops against the enemy from a defensive position, can be launched against the besiegers by the defenders. If the sortie is through a sally port, either to sortie or to sally can be used.

Military aviation

In military aviation, it is used to indicate the total usages of individual machines, so that (for example) one mission involving six aircraft would tally six sorties.

The use of the term for military aircraft originated in naval usage. In French, sortie literally means "exit". It has evolved to mean a short period of conflict, as in the time when the vehicles and vessels are away from their carrier or local berth.

Spaceflight

In spaceflight, especially for NASA's upcoming Constellation Program, the term sortie has been coined for a flight of the Orion spacecraft beyond the confluence of low-Earth orbit, such as a flight to the Moon or to the Sun-Earth L₂ Lagrange Point. This term was not used by NASA for the nine Apollo flights that flew by, orbited, or landed on the Moon between 1968 and 1972.