All of Stephen Stucker's lines as Air Traffic Controller Johnny were ad-libbed. (Source)

Lloyd Bridges, A.K.A. Steve McCroskey, was reluctant to appear in Airplane! because of his reputation as a serious actor. His sons, actors Jeff and Beau Bridges, talked him into taking the part. Cinema history thanks you, Jeff and Beau.
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"Jive Dudes" Norman Gibbs and Al White were the first and only actors to read for the part; they solidified a spot in the film by re-writing ZAZ's original dialogue, expanding it practically into its own language. (Source)

Airplane! made back its entire $3.5 million production budget within the first two days after it was released. (Source)