Talk about a cult classic. Actually—talk about classic classic.
Airplane! was an immediate commercial success on its release in the summer of 1980, and has only managed to grow in popularity and cultural importance in the 35 years since. On its 30th anniversary, distinguished news rags like the New York Times and The Guardian looked back on its zany comedy. It's often on the schedule of classic film festivals, with regular screenings here and there for hardcore fans and the newly-initiated. There are cast member "Where are they now?" articles, and endless websites analyzing just what makes the film so side-splitting hilarious.
On its 30th anniversary, Airplane! was added to the National Film Registry of the Library of Congress whose films are judged to be "culturally, historically, or aesthetically" important. (Re-read that oh-so-lofty description after you've watched the movie.) Seriously, every spoof movie since 1980 has Airplane! embedded in its DNA. Even if people don't dress up like Otto Pilot for Halloween or organize conventions like the Trekkies, the film's had such staying power since its release that every year the film makes new fans.
Even folks who haven't seen the film know the gags. "What's the vector, Victor?" "Roger, Roger." Say to anyone, "Surely you can't be serious," and there's a good chance they'll say, "I am serious. And don't call me Shirley." So much of the film's lunatic dialogue has entered the pop lexicon that if you're a fan of comedy, you're a fan of Airplane!