Factual errors: An ocean landing would certainly break up the fuselage of a 747. Even if it survived landing on water it could not sink in 5 minutes. An intact airliner with large air-filled compartments is much lighter than water.
Continuity: Just following the opening titles, Don Gallagher and Stan Buchek walk past the stationary 747 on the tarmac. Stripes are painted along the side and continue right around the nose of the aircraft. When the aircraft is taxiing prior to takeoff at night, the nose cone of the plane is shown painted black (i.e. a different aircraft).
Factual errors: When the stewardess puts the laserdisc into the player, she leaves the top door slightly ajar and the laserdisc will not play (even though it does in the movie).
Continuity: While the plane is loading all the crates- the plane goes from being outside to inside a hanger then back outside again.
Continuity: When the plane hits the oil rig tower, there is no damage to the wing in the very next shot.
Continuity: After hitting the offshore oil rig, the outer starboard engine (#4) is shown failing and taking fire. However, in the cockpit, Engine #3 (inner starboard engine) is shown failing with a skyrocketing EGT indicator (exhaust gas temperature), yet Engine #4's fuel cut-off and fire extinguishers are operated by the pilot.
Continuity: At the start of the film when the plane comes into land, it is a Boeing 747 in white coloring and a black nose tip, however later shots show a Boeing 747 in red, white and blue coloring and a grey nose tip.
Factual errors: The seats on board the executive Boeing 747 have no safety belts.
Factual errors: After submerging in the Atlantic, the captain said the airplane is "Pressurized". Of course, an airliner only pressurizes when the engines are running or when external air is plugged in, which is not the case underwater. It would fill with water in minutes after submerging.
Revealing mistakes: Just before one of the hijackers hits the on-flight security guard on the back of the head, you can see the actor playing the security guard flinch before he is actually hit on the head.
Revealing mistakes: When Gallagher and Buchek are exiting the rear cargo door of the aircraft (while it's being loaded in the hangar), the "American Airlines" logo on the 747 is clearly visible on the rear vertical stabilizer.
Continuity: When the Captain is rescued from the raft after escaping the downed plane, one of the Navy crewman (operating the outboard) is shirtless and wears a life vest. When they arrive back at the ship moments later, he has apparently removed his life vest and put both his shirt and the vest back on, as both crewmen now wear shirts.
Continuity: When the tail of the 747 strikes the water for the first time, engines 1, 2 and 4 are already missing. Number 3 is still intact and mounted on its wing pylon.