Factual error: When John Kostler arrives in New York from Massachusetts, they pan out and show him crossing the Brooklyn Bridge. There is no logical way, on the route to Manhattan from New England, that one would cross this bridge. It would require him to travel completely out of the way, and judging by the competence of the protagonist, it becomes obvious this was used for visual effect only.
Factual error: Cell phone signals are repeatedly blocked by electromagnetic radiation from the sun. However, GPS devices, which receive a much fainter signal from satellites, continue to operate. For that matter, television broadcasting, which relies on satellite relays, continues until the end of the film.
Factual error: Almost at the end of the movie, when John is driving in a crowded street just before joining with his parents, there is a shot showing a Water Delivery Service Car fully charged which is not possible due to the emergency. It is supposed to be empty because of people taking water for themselves.
New this month Factual error: The 9/11 death toll of 2996 - which John Koestler notices on the sheet of numbers - is the overall total for that day's attacks. But it is next to New York's co-ordinates, and the other attack sites have their own entries with locations and death tolls.