Factual error: Near the beginning of the film before James McAvoy heads up to the house for the evening meal, he is seen looking up through a skylight when a Lancaster bomber slowly flies overhead. At the time it was was supposed to be 1935. The Lancaster bomber did not fly until the beginning of 1941. Can't be an Avro Manchester either, they only had two engines and first flew in 1939.
Factual error: As the 1st Battalion, 7th Cavalry lifts off from LZ X-Ray at the end of the battle, it can be seen that there are no more American troops left at the battlefield. However, by the time 1/7 CAV left LZ X-Ray, it had been relieved by two full battalions (2/7 CAV and 1/5 CAV). There were around 700 American soldiers occupying LZ X-Ray by the time 1/7 CAV lifted off.
Continuity mistake: In the opening scene, Gunnery Sgt. Hartman is making his speech and passes by Privates Cowboy and Joker on his way to the other side of the barracks. On his way he passes Private Pyle standing to the right of Private Joker. Later in the scene, when he rushes over to confront Private Joker and then moves on to Private Cowboy and then Private Pyle, Private Pyle is on the left of Private Joker. (00:02:00)
Factual error: The boys go deer hunting somewhere in the Appalachians, but the geology is all wrong. That scene is in North Cascades National Park in Washington State. In addition, the "deer" they are hunting is a Red Stag. Not typically found in the Appalachians.
Revealing mistake: In one of Pickett's charge scene the bayonets are obviously rubber.
Factual error: In the final scene there is a shot which shows a Land Rover in the distance. Land Rovers were not built until after World War 2.
Factual error: They hold a huge dance in the hangar at night, and Dennis leaves to walk to the Memphis Belle through the hangar doors, which are wide open. The whole flight line, tarmac and hangar are bathed with light - on a US Air Force base in East Anglia during the blackout. Blackout restrictions were rigidly enforced and were not eased until September 1944. The last mission of the Memphis Belle was in May 1943.
Continuity mistake: The soldiers takes off from the aircraft carrier in Boeing CH-46 helicopters. In the next scene they are flying towards the target and the helicopters are magically upgraded to the Boeing CH-47 model. The mistake is clearly seen when counting the landing gear on the two types. The CH-46 has a single front landing gear and the CH-47 has a double landing gear in the front.
Revealing mistake: Near the end of the film, there is a football game played between the rival MASH units. Although the game is supposed to be taking place in a remote location of Korea in 1951, late model 1960's automobiles can be seen driving on a nearby highway as the game progresses. This gave away the fact that the football scenes were shot at a university in Southern California.
Plot hole: Radl and Steiner discuss the entire scheme to kidnap Churchill on the Alderney docks - in full view and hearing of a number of civilians (who shouldn't be there, pace another posting), including local fishermen. Though the Germans banned all fishing activities in the Channel islands including Alderney in 1941, they were well aware that there was a flow of information from the island to military authorities in the mainland. Why would they be so stupid as to discuss a top secret military mission in public? In reality, they wouldn't even discuss it in front of their own men.
Factual error: Towards the end when the cavalry uncovers the American flag, it has 50 stars.
Factual error: Toshiro Mifune's character, Kikuchiyo, travels to the bandits' camp and steals one of their two remaining fuselock muskets. Shortly afterward, the bandits fire twice at the samurai within five seconds with their last firearm. A fuselock takes as much as two minutes to reload, prime, and fire.
Visible crew/equipment: In the scene near the beginning of the film, when the 2 brothers are fixing to leave to join the army. After the mother gives them the flag, the shot changes to the 2 brothers. You can see the boom mic and the camera in the reflection of their shiny brass buckles.