Flying is the repetitive background tune that plays during all of the missions in 1942 (NES). It's basically a 15 second drum track with fragments of Morse Code embedded into the song. However, the Morse doesn't seem to spell anything in particular. Even worse, because the sound effects use the same channels as the music, it's constantly interrupted by gunfire and explosions.
Flying is an unofficial name, Ayako Mori should be contacted and asked for an official name. It is track 1 in the NSF file.