"act of flying," Old English flyht "a flying, act or power of flying," from Proto-Germanic *flukhtiz (source also of Dutch vlucht "flight of birds," Old Norse flugr, Old High German flug, German Flug "flight"), from Proto-Germanic *flugti-, suffixed form of PIE root *pleu- "to flow."
Spelling altered late 14c. from Middle English fliht (see fight (v.)). Sense of "swift motion" is from mid-13c.. Meaning "an instance of flight" is 1785, originally of ballooning. Sense of "a number of things passing through the air together" is from mid-13c. Meaning "series of stairs between landings" is from 1703. Figuratively, "an excursion" of fancy, imagination, etc., from 1660s. Flight-path is from 1908; flight-test (v.) from 1919; flight-simulator from 1947 (originally in rocketry); flight-attendant from 1946.