The narrative structure of Airplane! is tight, clear, and clean, consisting of a steady chronological plot with the occasional flashback to develop character. The story is lifted straight from Zero Hour!, a film ZAZ found as a result of their usual material-generating strategy—taping movies on late-night T.V. and then fishing through them for material. It "was like seining for fish," creator Jim Abrahams remembers. "We'd throw our net out at night and just record stuff—whatever was on TV, it didn't matter—so we'd have grist to make fun of." (Source)

As they later realized, ZAZ struck gold in Zero Hour!, not just for the joke potential, but for the narrative itself. "It's a perfectly classically structured film," Jerry Zucker notes, with complex characters and a gripping story in three acts.
(Source) ZAZ have acknowledged that they haven't had a better plot since, realizing the genius of Airplane! doesn't exist solely in its humor, but from its use of such a tried and true narrative, a strong spine on which the gags could hang. (Source)

Zero Hour! is based on a teleplay by prolific writer Arthur Hailey, who actually served in the Royal Air Force as a pilot. It's an archetypal, three-act story with a troubled hero who overcomes his demons in order to get back the one he loves, saving the day while he's at it. The feature film adaptation was a little on the melodramatic side, but the story itself is strong: a fact ZAZ benefited from without even knowing it.

"We weren't screenwriters at all," Abrahams once said. "We were joke writers." (Source)

So between the strength of Hailey's narrative, and ZAZ's knack for jokesmanship, Airplane! succeeds in blending archetypal storytelling with gag after gag of surrealist hilarity, proving that comedic filmmaking is about more than just the punch line.