Continuity mistake: The plane we see at the end dragging on the ground and taking off is a 707. 707's have four engines: two on each wing. However, the plane we see in the air is a 727. 727's have three engines: one on each side of the rear fuselage and one on the vertical stabilizer. (00:08:10 - 00:27:10)
Suggested correction: The exterior shots are all of a 707 (2 engines on each wing) until the very end of a movie. After Otto and his wife take off again, a 727 is flying away, but only that once.
Revealing mistake: When the plane crashes through the glass at the beginning of the movie, you can't see any wings on the plane. (00:04:30)
Suggested correction: Wings don't sprout out of a plane's nose. They would be significantly further back on the fuselage and out of sight.
Except you can see on either side of the nose, there's nothing blocking the view of the wings. There's no way for them to be so far back that you couldn't see them.
Other mistake: When Johnny reads in the folded newspaper, 'There's a sale at Penny's!', the viewer can read the headlines right way up - which means, from his side, he is holding the paper upside down.
Suggested correction: It's a reasonable bet that this was done deliberately as a sight gag. Throughout the movie, Johnny is portrayed as being somewhat 'special'.
