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Director John Hughes was known for staging improvisational moments for his actors in order to capture a genuine reaction. Since he was not satisfied with the Owen scene introductions after several takes, he privately instructed Dylan Baker (Owen) to wipe spit in his right hand just before shaking hands with Neil Page. Steve Martin was not expecting this, thus his disgusted reaction to shaking Baker's saliva slathered hand. The film crew reportedly exploded in laughter as Martin ran off to wash his hands immediately following the encounter. Hughes got the reaction he needed and the footage was kept in the film.
John Hughes, in an interview on the "Those Aren't Pillows" DVD, said he was inspired to write the film's story after an actual flight he was on from New York to Chicago. The flight was diverted to Wichita, Kansas, taking him five days to get home.
The exterior of their aircraft in flight is a re-use of the 707 flying through the storm from the movie Airplane! (1980), also released by Paramount Pictures.
On instruction from John Hughes, Edie McClurg's role as the St. Louis rental car agent was partially improvised. Hughes told her to simply riff a fake phone conversation with someone about Thanksgiving plans while Steve Martin remains waiting in line staring at her to finish up. McClurg came up with the idea to speak with her sister about who was going to make what adding "You know I can't cook!". Hughes asked her how she came up with those lines so quickly and she replied that, like his scripts, she just drew it from her own life. McClurg claims to this day that random people ask her to tell them they're fucked.
Steve Martin was convinced to join the production after favoring two scenes he had read from the script: the seat adjustment-scene in the car, and the F-word tirade at the car rental desk.