Goofs

(at around 1h 7 mins) When Sean asks the other passengers to block the stairs from the snakes they start unloading lots of bags from the overhead compartments although the top floor of the plane was originally empty except for the two agents and Sean.

(at around 1h 35 mins) Troy leaves the plane first on the escape slide. In the next shot he can be seen inside the plane again coming down the stairs behind the crowd waiting for their turn on the slide. The DVD audio commentary claims that this error was known but not deliberate.

(at around 1h 28 mins) The hole on the plane gets larger and larger, but the exterior shots continually show it at its first stage in circumference.

(at around 1h 3 mins) The aircraft is said to be "below nineteen-thousand feet", but the altimeter shows 37,000 feet.

Whenever there is a shot of the plane outside, no matter what point in the film all the lights are on, however numerous times, part or all of the plane had been plunged into darkness and it would cut away to outside and the lights would still be on.

(at around 1h 27 mins) Flynn tells the passengers to hold their breaths before he shoots the windows, thereby depressurizing the interior of the plane. In reality, if a person holds their breath during depressurization, a 'lung over-expansion injury' can occur. This is why scuba divers are taught "Never hold your breath".

(at around 1h 27 mins) If the aircraft did in fact undergo catastrophic decompression as shown, the cabin air would go milky white for a few seconds. This is due to the reduced pressure in the atmosphere bringing the moisture in the cabin to a point where it is visible, like when opening a soda can and seeing a brief flash of visible vapor.

(at around 1h 7 mins) When Flynn and Claire are trying to pull the aircraft out of the dive, the controllers readout shows the aircraft going from 1,344 feet to 591 feet in three second. This would be a descent of over 15,000 feet per minute, or at this point 2.4 seconds from impact. An aircraft of this size has too much energy at this descent rate to be leveled off before impacting the water.

(at around 35 mins) The flight attendant is shown entering the cockpit through the use of a keypad on the forward wall next to the cockpit door. There are no keypads in actual aircraft as that would defeat the purpose of having a security door, since a hijacker could possibly get the code by watching the crew enter, or by forcing a cabin crew member to open it under threat. The cockpit door is controlled electrically (or mechanically) by the flight deck crew only. This is a requirement of the hardened cockpit door design.

(at around 31 mins) When the aircraft loses power, the cabin is shown to go completely dark. This would not happen as these size aircraft have emergency lighting in the cabin and on the flight deck which is activated by the loss of normal aircraft electrical power. They are self contained battery types, they come on automatically and remain activated until turned off by the crew, and there are numerous independent sections of them on an aircraft.

(at around 4 mins) A shot of the baseball bat used as a murder weapon shows it to be a hollow tube.

(at around 23 mins) An altimeter is shown inside the box with the snakes triggering the clock which opens the box 2hrs later. Altimeters calculate the altitude based on air pressure, and since in airplanes like this the whole interior including cargo area is pressurized, an altimeter would not show 30-35,000 feet, only 5-7,000 feet.

A real non-venomous scarlet king snake is used in place of a venomous coral snake for some scenes. However, when a CGI coral snake is used, it still has the coloration of the non-lethal scarlet king snake. Since a CGI snake is not at all dangerous, it would have been more accurate to use the coral snake's correct coloration.

(at around 1h 30 mins) When the aircraft comes to a stop off of the runway, no engine sounds are heard, even though the engines would be running and shutting down the engines has not been addressed.

(at around 28 mins) When the couple is in the lavatory to join the "Mile high club", the guy reaches up and pulls out the smoke detector located in the ceiling so the couple can smoke a joint. Tampering with the smoke detector in this fashion triggers an alarm to the crew as this is a federal offense, and would be immediately investigated.

(at around 1h 35 mins) The herpetologist, Dr. Price, is shown giving medical directions to the paramedics when the passengers are coming off of the aircraft to be treated. He is identified as "the leading snake expert in the area", so most likely he would hold a PhD in the subject, and not an M.D. If he is in fact an M.D., he is shown to call out for "Lactine and Ringer's solution" to be administered. The actual term is either "Ringer's Lactate" or "Lactated Ringer's solution". This is a standard and common IV solution, and an M.D. would never make a mistake in something as common as that.

(at around 13 mins) Just before takeoff, some personnel pass the information "Flight 121" to identify the target-plane via radio to the killers. In fact, the special luggage with the snakes would not be able to change planes any more at this time.

Under no circumstances will passengers find out about an overbooked flight during the boarding process. This is something they will find out about during check-in. In addition, the first class passengers would have questioned this claim. At the gate area they would have been able to determine if this a lie, based on the number of passengers lined up to board in the first class line.

Even if Eddie Kim were sent to prison for life, he could still arrange for Sean Jones to be killed out of revenge, so testifying against Kim won't protect Jones.

(at around 56 mins) Agent Harris tells Dr. Price that they've already lost over 50 people. At that point, we have only seen 14 people killed, and in total, only 31 were killed. (26 from snakes and 5 from other phenomenon).