Factual error: The German fighters depicted in the film are Messerchmitt Bf 109 G-6s, and every single one of them is using the Rüstsatz VI gun pod, that is, 2 extra 20mm Mg 151 cannons. The Luftwaffe only equipped their Bf 109s with the gun pods when they were going to intercept bombers. In this movie, even on the fighter vs fighter missions, they have these gun pods, which is inaccurate, because the gun pods dramatically reduced the turning performance of the Bf 109s.
Factual error: When Maya and team first enter the hangar at Area 51 to see the helicopters, mechanics are working on them with socket wrenches. However, when they use the socket wrenches, they turn them one way to make the ratchet sound, then lift the wrenches up off the bolts to put them back in their original position, and do it again. In fact, the way they are holding the wrenches with both hands indicates there might be no bolt there at all. In other words, they are doing absolutely nothing...just making a ratchet noise.
Continuity mistake: The German and British airmen are looking at the Northern lights. From the rear the men are apart, but the front shots of them show them much closer to each other.
Character mistake: It's said in the movie a vice presidential candidate never gave a concession speech. Geraldine Ferraro did this in 1984.