Factual error: The space shuttle is spinning due to a stuck thruster. In such a case, the spin would be continually increasing as there is no air resistance. The X-Men shoot out of the thruster and the spin stops. Not factual. They would have needed opposite thrusters to stop it. (00:11:55)
Factual error: Erik arrives in Argentina at a place called Villa Gesell, shown to be a town in middle of mountains. Villa Gesell is a beach town on the Atlantic Ocean coast, with no mountains.
Factual error: The helicopter markings and paint schemes are exclusive ONLY to POTUS (President of the United States). Senator Kelly, even thought he's trying to get a Presidential bid, wouldn't be allowed to fly around in aircraft marked like that. (00:30:10)
Factual error: In the Shinkansen fighting scene, the railway line is seen having color light signals along its way. But the Shinkansen uses a signalling system that doesn't involve the use of light signals at all.
Factual error: When Magneto enters RFK stadium, a groundskeeper is lining a baseball field. RFK stadium did not host baseball in 1973, as the Washington Senators had moved to Texas to become the Texas Rangers after the 1971 season. In 1973, the only team playing in RFK regularly was the Washington Redskins of the NFL. In addition, the Paris Peace Accords were signed in January of 1973; so there wouldn't be green grass inside the stadium, regardless of what sports were being played there.
Factual error: When Wolverine leaves one of the compounds, he slashes through the door with both hands, creating an "X" in the door. After the second slice, the portion of the "X" where the cuts actually crisscross remains in the door, when in reality the pieces would fall out as they wouldn't be attached to the door any longer and would be floating in air. (00:44:30)
Factual error: Logan and Laura emerge from an urgent-care clinic in a small town, presumably somewhere in the Great Plains or eastern Rockies. Shortly after they emerge from this clinic, a Louisiana state highway sign is visible in the background. As the scene ends, the camera pulls back to show mountains in the background, indicating that they aren't in Louisiana.
Factual error: When Deadpool is starved of oxygen, then causes an explosion, it is implied that the excess of oxygen, coupled with a heat source (match), causes the chain reaction which blows up the oxygen tanks. However, for a chain reaction to occur, fuel is also needed. Combustion is an oxidation of fuel. The only fuel present which is hot enough is the match. The hoses/ pipes and the tanks would not be flammable.
Factual error: In the scene where Wolverine is shot in the head the bullet stays in place until it falls off. Wolverine's skull is indestructible Adamantium (that doesn't even bend slightly from the impact), and an object that applies a certain amount of energy towards another object has the same energy applied to it in return. Considering the bullet's high speed (which means high energy) and the fact that there is not enough material around Wolverine's skull to absorb the bullet's energy, the bullet should have bounced right out.