Is it ensure, insure, or assure?
"act of flying," Old English flyht "a flying, flight," from Proto-Germanic *flukhtiz (cf. Dutch vlucht "flight of birds," Old Norse flugr, Old High German flug, German Flug "flight"), from root of *fleugan "to fly" (see fly (v.1)).
Spelling altered late 14c. from Middle English fliht (see fight (v.)). Meaning "an instance of flight" is 1785, originally of ballooning. Meaning "series of stairs between landings" is from 1703.
"act of fleeing," from Middle English fluht (c.1200), not found in Old English, but presumed to have existed. Related to Old English fleon "flee" (see flee), and cognate with Old Saxon fluht, Old Frisian flecht "act of fleeing," Dutch vlucht, Old High German fluht, German Flucht, Old Nprse flotti, Gothic þlauhs.
A hallucinogenic drug experience; trip (1960s+Narcotics)