Factual error: A couple of times during the film, someone exclaims in horror that if this-or-that system fails, they will have to land the shuttle dead-stick (unpowered; no chance to veer off and try again). Actually, all shuttle landings are dead-stick; they are computer guided but nevertheless are unpowered, one-shot deals.
Factual error: At the end, the russian satelite is aimed straight at the moon. It couldn't have been done that way, and if they did aim at the moon, they would have had to aim to where it would be in 3 days.
Factual error: This line of thinking is repeated twice, once by the NASA scientist and once by the Tommy Lee Jones character: "To get to the moon, you only have to go halfway - gravity will take you the rest of the way". Actually, since Earth's gravity is 6 times greater than the moon's, you would have to go 6/7ths of the way, otherwise you return to Earth.
Factual error: The X-2 only had one seat. In fact, I don't believe there were any two-seater "x-planes".
Factual error: In the shuttle landing sims, the pilot is flying, not the commander.
Factual error: At one point, the rotating solar power panels on IKON slam into the Shuttle, wrapping around the nose. That's bad for the astronauts! The tiles all over the Shuttle are used to absorb the tremendous heat of reentry. They are also very brittle. An impact like that would have torn them off by the hundreds, making reentry impossible.
Factual error: The shuttle re-entry being nose-down could never happen. You had to hit the atmosphere nose-up so the ceramic tiles took the heat.
Factual error: Before launch, Flight reads off the names of positions and then "go". During a shuttle launch, Flight reads off the names and the controller checks in with a go/no go.
Factual error: In the opening scene the x-plane approaches at a very high speed and abruptly makes a very sharp turn to climb straight up. Even with pressure suits this high-speed maneuver would not only kill the pilots but snap the wings off the plane as well. X-planes were carried up to high altitudes before their engines were ever lit up. Flying an x-plane at ground level just was not done.
Factual error: The superfortress has a near miss with one of the pilots who has not opened his parachute yet and is therefore still in free fall. As seen from the ground the superfortress would be just a dot in the sky, and the pilot would not yet be visible to the naked eye. Jerry says he saw it happen and he is not even using binoculars - no-one has eyesight that good.
Factual error: When they first go EVA to look at the satellite, Eastwood goes into the Shuttle cargo bay to put on his Manned Maneuvering Unit (MMU). He goes outside without being tethered at any point. Even when deploying an astronaut in a MMU, the astronaut remained tethered until he was safely mounted into the MMU, then the tether was removed. Upon his return, the astronaut was again tethered before he dismounted the MMU.
Factual error: The Russian says that the missiles in IKON are locked onto American cities. The implication is that those cities will be destroyed if Eastwood screws up. Actually, since the orbit has decayed from geosynchronous (an altitude of roughly 22,000 miles) to low Earth orbit at 1000 miles, I don't think the missile guidance systems would get a chance to work. If the missiles were launched, they would simply shoot down toward the Earth and blow up wherever they happened to be. So, prayers to anyone unlucky enough to be directly below those missles.
Factual error: Several times in the film you see astronauts "suit-up" and head straight out the airlock into space. In reality they would have to pre-breathe pure oxygen for forty minutes to purge the nitrogen from their bloodstreams. If they just went straight out they would suffer from "the bends", as divers do.
Factual error: When the super fortress has a near miss with one of the x-plane pilots the pilot should be in free fall and not appearing to float motionless as the super fortress passes by.
Factual error: After bailing out one of the pilots somehow suspends his free fall and is almost hit by the B29 while motionless in midair.
Factual error: Clint Eastwood and Donald Sutherland go scooting around in open space (admiring a view of Italy on the sunlit side of the Earth) with their gold solar-screen visors retracted wide open. To avoid accidental instant blindness, real astronauts would never open their solar-screen visors during EVA on the sunlit side of the Earth; yet the astronauts in this film do it constantly, with no ill-effects.