Flyboy was a slang term for a pilot or airman.
In 2378, B'Elanna Torres referred to USS Voyager flight controller Tom Paris as a flyboy three times, once calling him a "Starfleet flyboy". She characterized them as being "all the same" and joked that upon returning back home, he'd abandon her and their daughter for the next piloting assignment that came his way. Paris assured her he would never do that. (VOY: "Endgame")