Although the plane crashed into the water, none of the survivors seemed to have got the least bit wet.
When Steve gets out of the car to change the flat tire, he's wearing black leather boots with a stacked heel. On the island he is wearing black sneakers.
At the plane drop the two bad guys obtain two automatic pistols, and during the night time shoot out, one is now clearly using a revolver.
The military personnel are wearing the pre-1969 uniform jackets, with external flapped lower pockets and no name tag above the right breast pocket. By 1969-70, the US military had updated the service jackets. The lower jacket pockets were internal and all military personnel now wore a plastic name badge above the right breast pocket.
At 41,000 feet altitude the plane would be way above any thunderstorms.
At 15:16 after announcing to brace for a crash landing one can hear the landing gear dropping. An experienced captain would never drop the landing gear while attempting to "ditch" the plane onto the sea.
When the Major and the Commander are looking for firewood, they uncover a snake. The Major identifies it as a "black phase snake." The black phase snake is a known color morph of the Timber Rattler, a snake which is indigenous to the American South East. It would not be found on a Pacific island, which is where the plane's survivors ostensibly are.
Reflections from the overhead movie lights are clearly visible as bright round spots on the shiny metal skin of the downed plane a few moments before the passengers start exiting from it.
At the beginning when Steve changes the flat tire he makes a hydraulic gun sounds typical of a mechanic's garage. A bionic hand removing the nuts would not make such a sound.
When the pilots call to change altitude to 41,000 feet, they ask for "Flight Level 41". Flight Levels are every 100 feet. The pilots should have asked for "Flight Level 4, 1, 0".
Steve Austin mistakenly identified the plane dropping supplies as a C-133, it is actually a C-119.