One of the characters is listed as a B-51 Pilot. The B-51 was a low flying fast attack jet bomber that had not been invented yet (as opposed to the high flying famous B-52) The production probably meant "P-51" pilot, which was the famous "Mustang".
When the B-17 goes down, the radioman uses the plane's nickname instead of its call sign when sending out a mayday. Further, the mayday is sent over a voice radio which was used for short range communications between aircraft. A mayday would be sent using Morse Code with a long range radio.
The B-17, unlike the later B-29, was not pressurized. The B-17 pilot, early in the film, says they are flying to 20,000 feet - and yet the crew is not wearing oxygen masks. These are required if you fly much above 12,000 feet.
The airmen use the term UFO when the term UFO wasn't invented until 1952."Use of "UFO" instead of "flying saucer" was first suggested in 1952 by Capt. Edward J. Ruppelt, the first director of Project Blue Book, who felt that "flying saucer" did not reflect the diversity of the sightings.
The two SAS soldiers are wearing the wrong colour berets, their beret pins are on the wrong side, the berets are pulled down on the wrong side, and their patches show them as being part of the current British Army Parachute Regiment 16th Air Assault Brigade, which uses the Pegasus badge to denote the assault on the bridges of Arnhem and Nijmegen (as seen in the film 'A Bridge Too Far'). In addition to this, the rank badge shown on the collar is a US Officers rank badge, and not a British one.
The Army Airforce flight personnel are all wearing infantry badges on their lapels. The AAF's badge was a winged, two-bladed propeller. Also, the uniform jackets are the wrong color and cut; they look like surplus Yugoslav or Bulgarian army tunics.
The commanders in England speak of "mounting rescue missions" for downed flight crews as if they were routine actions. Crews shot down over enemy territory were considered lost. Rescue efforts were not expected or performed.
In the church when the exposition about the gargoyles occurs, the girl states that the small ones are "flesh and blood"; yet, moments before one was hit by a shotgun, and shattered as if made of stone.