Military aircraft were any type of aircraft utilized by the military for various mission profiles.
While traveling to the surface of Gosis' species homeworld aboard a shuttlepod to retrieve a missing communicator, Lieutenant Malcolm Reed reported to Captain Jonathan Archer that there were three military aircraft ahead located 72 kilometers off starboard, advising that they should increase their descent vector in order to keep the shuttle below the aircraft's visual threshold. (ENT: "The Communicator")