Errors in geography: Israeli signs, etc at "Beirut" International Airport. Most noticable: El Al planes, 'Meshteret Israel' or 'Israeli Police' at the gate, and 'Brochim Ha Baim" or "Welcome" at the gate.
Revealing mistakes: In a scene when McCoy is searching the bed room, he removes a mattress and a terrorist that is hiding underneath get a shot off. The terrorist hits the lens of McCoy's wrist mounted flashlight before being shot. Shortly there after, you can see the flashlight again, only the lens is intact.
Continuity: After the plane has been hijacked and various shots of Washington D.C. are being shown, there is a shot of the Pentagon. The date and time is shown. The time reads 2:15 AM and yet it is clearly a sunny day in the scene.
Errors in geography: When the Delta Force arrives at the airport to leave country, they sneak through a cotton field, Lebanon does not have such fields, Israel does.
Errors made by characters (possibly deliberate errors by the filmmakers): Captain Campbell announces over the P.A. that the flight time from Athens to Rome is 55 minutes. While a flight between those cities would land 55 minutes later in Rome due to the time zone difference, the actual flight time would be of 1 hour 55 minutes. (Even at the Boeing 707's maximum speed of 620 miles per hour, an actual flight time of 55 minutes would be impossible because of climb and approach speeds, etc.)
Factual errors: Upon arriving in Algiers, Lee Marvin's character puts an American flag patch on the left shoulder, with the blue field to the rear. That patch would be worn on the right shoulder. The blue field is always towards the front.
Revealing mistakes: After the colonel prevents the Delta Force from ambushing the plane, the head terrorist brings the bloodied navy member to the plane door and shoots him, dropping him to the pavement. When the man checks his ID and discovers who he is, on the last shot, you can clearly see the dead marine breathing.
Continuity: Norris' footwear switches between combat boots and black sneakers several times during the film.
Continuity: On the scene where Norris mets the convoy of terrorists (holding the main hostages), he blows up the first car in the convoy and then rides past the convoy and skids to face the end of the convoy. Before he skids you can clearly see tyre marks on the roads from when this has been attempted more than once.