Factual error: At the beginning of the movie, Steve Martin is trying to catch a cab to LaGuardia at about 5:30PM. In the movie, it's still daylight, whereas in reality, NYC is pitch black by that time of day - the sun sets at about 4:30PM in late November.
Factual error: If they are really in the Wichita, Kansas airport, listen carefully to the airport announcements (real faintly in the background). When they say for "Mary Ellen" to meet her party upstairs, there's a slight problem with that. There is no upstairs in the Wichita airport. (00:12:53)
Suggested correction: There is an upstairs. You enter the terminal on the ground floor and go up for security and the gates.
Factual error: At the very beginning of the film during the boardroom scene, Steve Martin checks his plane ticket. Departure time on ticket from NYC is 6:00pm. Arrival time to Chicago is 6:45pm. Travel time from NYC to Chicago is approximately 2.5 hours. Arrival time after time zone change should be approx. 7:25pm, not 6:45 pm. (01:31:25)
Suggested correction: Unsure about plane travel time in the 80s. But it currently takes 90 min to travel from DC to Chicago, and the airlines usually add a buffer. So this trip would most likely arrive at 6:30 CST, and a 15 min buffer time would still be reasonable (6:45 pm). For example, my plane tickets usually say estimated flight time of 1:45 or 2 hrs, but when the air currents are normal, it takes 90 min. DC is slightly further south than Chicago, while NYC is slightly further north.
Suggested correction: Considering from Los Angeles-Chicago is a 4-hour flight, and LA-New York is a 5-hour flight, I don't see how it could take 2.5 hours between New York and Chicago. Seems like 1-1½ hours is more accurate.
Factual error: In Wichita, when Del and Neal are getting picked up by Owen at the Braidwood Inn, there is a mountain right behind Owen. There are no mountains in Kansas.
Factual error: In the scene at the Braidwood Inn, after Neal shakes Owen's hand and the shot is of Owen with the freeway in the background, you can see a Jays Potato Chips truck drive past. The inn is supposedly near Wichita, Kansas. Jays Potato Chips were not sold west of the Mississippi at the time.