Character mistake: The "MAC-10" machine pistol used by Darryl and Sergeant Murtough is actually a Cobray M11/9.
Character mistake: When Cutter is talking with Chief Biggs for the first time, right after the negotiations for fuel, Cutter says he is the former head of security for the airline. Since he has just been hired for that role (after being an independent security consultant), he should have called himself the future head of security, or new, or something of that nature. Former would indicate he has resigned from the position.
Character mistake: Lisa is testifying about the 1963 Pontiac Tempest and the 1964 Buick Skylark being the same height, width, and wheelbase. While the Tempest and Skylark shared the same components, the 1963 and 1964 models were quite different from each other. The 1964 Skylark and Tempest moved to a 115 inch wheelbase and a larger body and frame. The 1963 Skylark and Tempest were smaller with a 112 inch wheelbase. An expert as she claims to be wouldn't confuse the two.
Character mistake: When Greer and Cantor visit Ryan's home after Miller's escape, they state that he was being moved to HMP Albany on the Isle of Wight (correct, given it was a Cat A dispersal prison at the time and regularly used for IRA prisoners) however Greer later states "it happened in Kent, near the channel", which is incorrect. Lymington (as stated by the guards over the radio in the escape scene) is in southern Hampshire - over 90 miles away from Kent and on the other side of the country.