In one of Ted's war flashbacks, a Visa credit card can be seen. It has been 6 years since Ted last flew, meaning this flashback takes place in 1973/1974 at the earliest. At this point in time, Visa was still called by its original name, BankAmeriCard.
If Ted Striker flew in WWII (those are WWII airplanes), then he couldn't have joined the Peace Corps right after the war because John F. Kennedy didn't invent the Peace Corps until 1961. That means there is a 16-year gap since the end of the war in 1945 and the beginning of the Peace Corps. in 1961.
When Ted Striker is talking about the first time he realized he had a drinking problem, he is holding a bottle of Gatorade, which wasn't developed until 1965 and not marketed until 1967. Yet Striker said he and Elaine joined the Peace Corp. right after WWII, which ended in 1945.
During the fight between the two Girl Scouts at the Magumbo Bar, one girl scout is thrown across the bar and into the jukebox. When her head hits the jukebox window, the sound of shattering glass is heard, but it's clear that there is no glass in the window frame.
When the orderlies get out of the ambulance to take out the gurney with the sick girl on it, one of them almost trips over his own feet as he's opening the back doors of the ambulance (the blonde one, to the right).
After Elaine lets go of Ted in the dance floor, he somersaults into the audience, quickly gets up and runs back to the dance floor. But while "Ted" (the stuntman) is somersaulting, the real Ted (Robert Hays) is visible in the background.
During the opening montage when certain principal characters are introduced, Joey (the little boy) can be seen in the far background carrying a brown bag in the shot with the Hari Krishnas. A few seconds later we see him getting out of a car with his parents and luggage.
When he first begins to tell his story to the old lady there is a seatcover between the back of the two seats they are sitting on and the upholstery on both seats is the same. at the end of the story, the seat upholstery is different on both seats and the center seatcover is missing. The upholstery is the same and the center seatback cover is back however a bit later in the film when Ted is sitting next to Elaine.
One exterior shot as the plane is landing shows the silhouette of a Boeing 727, noted by the lack of engines on the wings and the two wheels (instead of the four that a 707, which other external shots show the plane as being, would have) on one "main" landing gear assembly. The shot at the very end (where the words "THE END" come up) also shows a 727.
During the 747-through-the-window gag, the plane is originally shown to be in period TWA colors, before it is misdirected. However, when it plows through the window, it has the fictional Trans American colors. Most obviously the red stripes now wrap all the way around the nose and the black anti-glare patch is missing from beneath the cockpit windshield.
When Striker unlocks the autopilot the plane takes a deep nose dive and the next scene is of the altimeter whirling around and around. In the same scene, however, the "flight level indicator" next to the altimeter does not show the plane descending at a steep angle. The next scene does show the Flight level indicator finally coming to a level plane.
When the plane lands, the landing gear collapses and the plane is on its belly when the passengers disembark. Later, when Ted and Elaine are kissing next to the plane, it is sitting on landing gear which is intact.
In the beginning when Striker pulls up in his taxi the available light on top is lit and then goes out when he opens the door, the light on cabs do not go out until the flag on the meter is dropped which did not occur until Ted reached back through the passenger side window.
Ted Striker throws a full glass of drink over his shirt and soaks it. The scene cuts away to the cockpit and then back to Striker (with the Sikh dousing himself in gasoline) and his shirt is dry again.
The plane is flying on a path that starts on the west coast and heads for Chicago, implying that the plane most likely starts in California or somewhere near there. However, the airport where the flight starts and the one where the plane lands are clearly the same airport.
Mandy, the flight attendant, is on board and in the doorway directing passengers to their seats in one scene, and then she is standing on the tarmac next to the gate talking to a man in the next when Ted Striker appears.
According to the dialogue, the airplane is supposed to land on runway 9 (niner), but the number 30 is clearly visible on the runway's threshold as the plane lands. There is no runway 30 at Chicago O'Hare airport.
Ted flips a switch after saying, "This must turn on the landing lights," and puts the plane into a nosedive, but the shot showing him turning the switch off is obviously on the radio as it has markings of "FREQ" (frequency) and "KC" (kilocycles). Flipping a switch on a radio won't send a plane into a nosedive. Additionally, the radio is too old for a 1980s aircraft because the frequency displayed is 1710 KHZ, which is an aircraft frequency long before 1980, when VHF frequencies would be used.
Although the plane clearly has jet engines, the engine noise heard inside the cabin throughout the film is of a piston-engined propeller plane. This engine noise is taken from the film Zero Hour! and is a long-running gag: Airplane! is a spoof of disaster films such as Zero Hour and Airport.
Despite what Ted Striker hears in his interior monologue, Pedro Borbon and Manny Mota were never on the same roster, so Mota could not have pinch hit for Borbon. This is simply a case of someone imagining what they think would be really cool instead of an actual case of someone recalling something that happened.
When the captain notifies Chicago of the emergency, he said nothing about food poisoning, however, the air traffic controller orders all meal services canceled. This could simply be because the character never did like the food on meal services, a way to comment on how lousy airline food really is, and not because of the food poisoning on the aircraft.
The model airplane that the pilots give to the young boy who tours the cockpit is not the same kind of plane that they are flying on. The model is a 727, the plane being used is a 707. The pilot never said that it was a model of the plane that they were flying.
On the phone, McCroskey orders all food service out of LA to be halted. However, no one had told him that the passengers were becoming sick due to food poisoning, so he would have no reason to halt the food service at that point in time.
When the two "Girl Scouts" are fighting, one is thrown over a railing and smashes a table. The fight continues, the other girl gets kicked backwards and out of frame, at which point she clearly bumps into the camera, causing it to wobble.
At the airport, when Oveur gets a call about the "transplantation-girl" (with the white/red/black phones), after he picks up the wrong phone, you can clearly hear Nancy Hansen (the script supervisor) laughing in the background.
In the scene where Dr. Rumak is treating the sick female passenger, he is removing eggs from her mouth. In one shot where he removes and egg, cracks it and a little bird flies away, the woman is startled and in her half-open mouth you can clearly see that an egg is already there, making it obvious that she was releasing the same egg time and again; equally obviously, then, the doctor was picking up additional eggs from underneath the tray table.