Continuity mistake: When Leelee Sobiesksi gets on the motorcycle with her husband, the baby's head cushion moves from full coverage of the baby's head to partial coverage, to full coverage, back and forth, several times.
Factual error: When the comet is passing through the atmosphere it shines about as bright as your average bike-light, and the shot shows thousands of people looking directly at it without shutting their eyes. When a comet of that size goes through the atmosphere it does so at an incredible speed. The friction between the air molecules and the comet produces a light many times brighter than the sun, anyone looking at it would be blinded instantly.
Continuity mistake: When Orrin the astronaut is saying his good-byes to his wife and kid, we see him reach out to the screen as if to touch them with his right hand. When we switch to the shot within mission control, he's reaching with his left hand.
Factual error: The shock wave that hit Messiah when it detonated the nuclear bomb on the comet would not have existed in space. It may have been hit by debris, but that would have destroyed the craft.
Other mistake: How can it be named Wolf-Beiderman? Wolf never sent the email, and even if it did go, once the network was restored, he never called it Wolf-B before writing it on the floppy label. The president says both were killed in the crash. So, they invent an astronomer working at the observatory and no one notices? Remember, the floppy was destroyed in the fire. Wolf never called anyone; he was killed while trying to make a call. Maybe the pics were also burned. Mr. Perry never followed up?
Suggested correction: We didn't see him send the email, but that doesn't mean it didn't happen. We know he sent it because it's stated that's what happened.
Factual error: A wave 1000' high would have obliterated the containments and wiped out the spent fuel pools of every nuclear plant on the east coast. Even if they were all shut down, there would be no time or way to remove all the fuel and no place to safely store it all if they did. There are thousands of metric tons of fuel that have to be actively cooled for years, otherwise it would all catch fire and burn, or at the very least boiled all its cooling water away and melted/uncovered it to allow gamma shine. This would have, in and of itself, made the northern hemisphere uninhabitable for several hundred human lifetimes.
Continuity mistake: When they are on the motorcycle near the end, he is first traveling with the flow of traffic that is stopped (west). When she gets on the bike with him and the baby, they keep going with the flow of traffic. Than the smaller asteroid enters the atmosphere, it is traveling in the same direction they are driving on the motorcycle. But when it passes the girl's family in the van, now the asteroid is traveling against the flow of traffic (east).
Continuity mistake: On the comet the screen shows the position of the vessel right at the sunlight line. A few moments later the position is shown as being on the far side of the comet away from the line, even though the comet didn't turn.
Continuity mistake: When the boy takes the motorbike from the garage the mirrors are out of line. In the next shot before he rides out, the mirrors are all in line.