Factual error: The three panzers that ambushed the Hellcats are supposed to be Mk. III's with the 50mm gun, but they only had 5 bogie wheels, instead of 6, and no driver or radio operator's hatches.
Factual error: Declan takes a gun from his glove compartment and nothing else. I counted that he fired 22 shots before being put down. There is no way that gun had a 22+ round magazine.
Factual error: The alien drops the video camera out of the UFO from outer space and it falls to earth landing on the ground. This very far drop would certainly have busted it to pieces, if not ignited it on reentry, but when the guy picks it up off the ground, it appears only the screen is cracked.
Factual error: Near the end of the helicopter scene Jenko pulls the pin of a grenade with his teeth before he throws it. It is not possible to pull a grenade pin with your teeth as it requires more force than that.
Factual error: The streak ended in '04, but at the beginning of the movie the seniors talking about their last game have letter jackets with the year '05 on the sleeve.