Continuity mistake: The size of the bed in Neal and Del's motel room changes overnight.
Continuity mistake: At the beginning, when Neil is racing Kevin Bacon for the taxi, he trips over the trunk and falls into the street, nearly being run over by a BMW. The car honks and pulls away. When the shot switches to show Kevin Bacon getting in the taxi, the car that almost hit Neil is now an Oldsmobile. (00:03:50)
Continuity mistake: When Dell and Neal are sitting on the side of the highway in downstate Illinois, the sign says "Chicago 102" in one scene and "Chicago 100" in another.
Revealing mistake: When Steve Martin first calls home to tell his wife that the flight is delayed we see a lovely, cozy picture of the Page family enjoying a delicious, home cooked meal. However, in the shot where the kids are all sitting at the table the youngest child (back to camera) is being carefully 'watched' by a woman who is sitting on the floor next to his chair. I presume it is the actor's mother making sure that her little baby doesn't fall off the chair...
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)
Continuity mistake: Right after the close call going the wrong direction on the freeway and Steve Marting pulls his fingers out of the car's dashboard. The following shots show John Candy releases his grip of the steering. The top of the steering wheel has been completely push forward. All remaining shots of the car show the steering wheel in perfect alignment.
Visible crew/equipment: When Neil exits from the airport just after the employer told him "You are f***ed", some onlookers and a crew member moving the camera on the dolly track can be seen reflected on the glass of the entrance from which Neil comes out.
Revealing mistake: When they are sitting in the bus station in Jefferson City - and then the next scene is the somewhat "speeded up" shot of the kid running up and down the aisles of the bus (before the "take a picture, it'll last longer" scene) - as the kid is running up and down the aisle, watch the woman in the front left seat. The handheld windmill that the kid is running with hits her in the head and her eyes "pop open" as to be surprised by the hit.
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.
Other mistake: When Neal checks his airline ticket it says he departs from N.Y.C. J.F.K. but the movie claims to have him flying out of LaGuardia.
Continuity mistake: When Neil is chasing the cab after Del stole it, the bags he is carrying change hands in different shots.
Continuity mistake: When Neal is racing Kevin Bacon for the taxi, he gets close to the cab and all lanes of traffic are at a standstill. Seconds later when he trips over the trunk, the lane he falls into is empty and a car has to brake hard to avoid hitting him, indicating it was travelling at speed already.
Plot hole: After the car burns, and they arrive at the motel, Neal only has $17.00 on him and nothing but melted credit cards, forcing him to give up his watch to help pay for the room. Del only has $2.00 but his watch doesn't quite flip the bill. At this point, between Neal and Del, they only have $2.00. However, when Neal invites Del into the room, so he doesn't freeze to death, they are eating Doritos and drinking shooters. Even in 1987 Doritos and a bunch of shooters must have cost more than $2.00. This is assuming Del didn't already have them in his trunk. But even if he did, at the end, Neal gets on his train, makes a return trip to find Del just where he thought he'd be, and then they'd both have to get back onto that train. After all, they both showed up at Neal's home. Once again, It would take money to get on that train. Four train fares with only $2.00. Neal's first trip, return trip, and Neal with Del for the last trip = four fares.
Continuity mistake: After leaving the El Rancho hotel. (when pulled over by the state police) Neil seams to find some new clothes, including a too small hunting hat, and scarf. On the walk home, Neil is carrying a large suit case, instead of his garment bag and brief case.
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.