Continuity mistake: After the hijackers have taken over the plane, the blond flight attendant's hair, styled in a French Twist, keeps changing from messy (presumably from the chaos) to as smooth and neat as when she boarded the plane. She's never offscreen long enough to have simply fixed it. Not until the passengers revolt does it remain disheveled.
Continuity mistake: In both the exterior shots during the film and in real life, the Boeing 757-222 (N591UA) operated by United Airlines is shown to have 2 doors forward of the wing. In the interior shots, the front door is shown, but between the first class cabin and the economy class cabin, there is just a partition, no door.