1870-75; < Frenchaéroplane, equivalent to aéro-aero- + -plane, apparently feminine of plan flat, level (< Latinplānus; cf. plain1), perhaps by association with forme plane; apparently coined and first used by French sculptor and inventor Joseph Pline in 1855
1866, from Fr. aéroplane (1855), from Gk. aero- "air" + stem of Fr. planer "to soar," from L. planus "level, flat" (see plane (1)). Originally in ref. to surfaces (such as the protective shell casings of beetles' wings); meaning "heavier than air flying machine" first attested 1873, probably an independent Eng. coinage (see airplane).