(at around 23 mins) As the jets are flying in close formation, the DC-9 pilot is told to "slow to 150 knots" and to "descend to flight level 140". Both of these phrases are incorrect. In the United States airspace system, the term Flight Level is only used at 18,000 feet and above - flight level is a measure of hundreds of feet (Flight Level 310 = 31,000 feet above sea level). There is no Flight Level 140; it would be expressed as 14,000 feet.
Stallone's character is seen wearing a wedding band in earlier scenes yet in the film he is not married. This is confirmed when he states that he's came back for Jessie, clearly his love interest but not his wife.
(at around 1h 35 mins) When Tucker helps Walker out of the water, Walker is soaking wet. We cut briefly to Qualen in the chopper, then when we cut back to Tucker and Walker, Walker is completely dry (even his hair).
(at around 29 mins) As the plane is crash-landing a rock clearly takes of the starboard wing and the rear third of the fuselage along with both engines which are behind as the forward section slides away. Seconds later as the fuselage is sliding to a stop we can hear the engines loudly "winding down" as if they were still attached.
(at around 20 mins) Shortly after Gabe returns from Denver, Jessie enters the rescue station while it is raining outside. Once she enters, it appears to be snowing through the back window of the station.
(at around 55 mins) When the villain with night-vision first opens fire on Gabe and Jessie, he is standing still. The next point-of-view shot through the night-vision goggles shows him to be moving toward his targets. A third shot shows him again standing still, in his original position.
(at around 28 mins) In preparation for the Jetstar emergency landing, Kristel tells the copilot to "lower the flaps 25 degrees." The copilot repeats "flaps 25 degrees, check," yet each shot of the place after this still shows the flaps fully retracted.
(at around 12 mins) The money was made in the Denver Mint, but the Denver Mint only makes coins. Banknotes are printed by the Bureau of Printing and Engraving, located either in Washington, DC or Fort Worth, Texas.
This film takes place in Colorado, in the Rocky Mountains. When the villains use night vision, it shows their elevation as somewhere in the 3,000 ft range. However, even the lowest point in the Colorado Rocky Mountains is well above 3,000 feet.
In several scenes where Qualen is flying the helicopter, he is either pointing a pistol or handing keys to Jesse. Helicopters are an intense two hand operation, especially in the hover, as the aircraft is shown doing several times. There are two controls, the cyclic and the stick, and he is shown taking his hand off the cyclic, which you could not do, particularly in a hover.
(at around 1h 35 mins) When Gabe falls into the water he performs a variety of moves including removing his shirts and taunting Travers. After he emerges with help from Hal, Gabe is fine and the movie goes on. This could not happen. The temperature of the water should have put him into shock and stiffened all his limbs shortly after he fell in. Not to mention, even if Hal were to take him out, Gabe's core body temperature would have dropped to the point of a hypothermia scare.
(at around 54 mins) The temperature in the night vision goggles shows as -11C (12F). They're not dressed to deal with that weather, especially as it colder at night, with an added wind chill, and no windbreak. They'd be dead from exposure very quickly.
When Gabe & Jessie disturb the bats, he urgently tells her to get down as if there is some danger. While she might freak out about a flock of bats flying around her (although this seems unlikely for the character) the bats would be largely avoiding them whether standing or crouching and even were a bat or ten to hit them accidentally it wouldn't hurt.
There are wolves shown attempting to attack a base jumper in the film. The grey wolf was extirpated in Colorado, the setting of the film, in 1940. While there are captive wolves in zoos and perhaps wolf dogs available to owners, there are no longer wolves in the wild in the state,
Despite the temperature being well below freezing, there are no visible indicators of the cold temperature, such as the characters' breath being visible, or reddened skin in the face due to the wind and cold.
The goof item below may give away important plot points.
(at around 1h 24 mins) When Qualen kills Kristel at the helicopter he lets her body slide backwards off the pan. Her feet can be seen to kick up in the air as she falls on her back. Impossible if she is dead.