When Chance Buckman flies his jet and talks to Greg, a rear view of the cockpit shows the doorway to be clear while a view from inside the cockpit shows a curtain over the doorway.
During the opening night scene when the oil well fire begins which triggers the action of the story, numerous trees can be seen fairly close to the burning oil well. A few minutes later when Buckman's fire fighters arrive, the burning well is on the banks of a small lake or pond surrounded by oil wells. There isn't a tree within sight of the well. The first scene of the well explosion was clearly shot in a different location.
When Tish first arrives at her father's apartment in Houston, she asks for a scotch rocks, but in numerous shots, there is never any ice in the glass.
At beginning of the movie after helicopter lands, speed of rotor blades varies between shots.
When Chance and his crew are in South America and are attacked by machine gunfire by the rebels, the number of bullet holes in the office door varies from 3 to 5.
Chance remarks about a "poison well" spewing "hydrogen sulfate." It is actually hydrogen sulfide which is most often found in oil well situations. Hydrogen sulfate describes the compound which is sulfuric acid and is generally not gaseous. Hydrogen sulfide is a gas and it is poisonous.
The Australian driller takes off his mask a decent distance away from the poison well fire and dies nearly instantly. Yet Greg is right under the well and has a hole in his hose going directly into the closed environment of his mask and is only knocked out.
However, this can be explained by the Australian breathing air that had been saturated with the poison gas. The gas was spreading past the safety flags, possible due to wind or other weather conditions. Greg was working with an air mask. When his hose split he still had some air left in his tank that would have been at a higher pressure than the outside air, keeping it out of his breathing air to a degree. He is seen putting his hand over the leak and then passing out in the water. The water would have prevented further poisonous air from getting into his system.
During the office scenes, looking through the office window, obvious toy cars were used to simulate the highway (that could be seen from outside when the helicopter first landed).
When Chance Buckman talks to Lomax, Tish and Greg in the hospital room, there's an obvious long reverb on their dialogue every time they speak loud or yell. This is a clear indication for the fact that the room is a partly open set built on a large sound stage, which accounts for the reverb. The same goes various other indoor sets.
When the Hellfighters are fighting the first oil well fire, they explode nitro glycerin over the oil rig to extinguish the fire, but after the explosion, the fire is still burning.
Madelyn picks up Tish from the airport. Tish changes her mind and needs to go back. When Madelyn throws the car in reverse, the rear projection showing the traffic behind them shows the car going backwards before the actual car supposedly starts moving.
When the big cargo plane lands, the sound of the wheels touching the runway is heard seconds before any of them actually contact the ground.