Not scheduled; spec. (in later use, of an airline) operating without fixed or published flying schedules; of or relating to such an airline.

A written evidence, instrument, or contract executed between man and man. Used attributively of or pertaining to an aircraft hired by contract…

Designating a system whereby unreserved or unclaimed places (originally for air travel, later also for other forms of passenger travel, or for…

Originally U.S. Relating to or designating a transportation service (esp. an airline service) for which prior booking is not required.

U.S. colloquial. A flight on which a passenger cannot expect to get much sleep because of the time of departure or arrival, esp. an overnight flight…