flying (adj.)early 15c., replacing forms from Old English "flying, winged;" present participle adjective from fly (v.1). The meaning "attached so as to have freedom of movement" (1670s) is the source of the nautical use (, etc.). Meaning "designed for rapid movement" (especially in military terms) is from 1660s; meaning "passing, hasty, temporary, rapidly constructed" is from 1763.
is from 1510s; is from 1660s. , ghost ship off the Cape of Good Hope, is attested since 1803 [John Leyden, "Scenes of Infancy," who describes it as "a common superstition of mariners"]. (1706) probably is from the image of a naval vessel with the national flag bravely displayed. is from 1736 as a theoretical device. first attested 1947, though the image of saucers for unidentified flying objects is from at least 1880s.