Just before the infected come over the wall in Jerusalem, Gerry says, "If I could get into India, where would I start?" "India's a black hole." The lines originally named Russia, not India, and you can still read Russia on his lips. The editing of the scene fails to completely conceal the second overdub as well.
At the beginning of the film, in the traffic jam, a motorcycle policeman pulls up and tells Gerry to get back in his car; there is nothing behind him but gridlocked traffic; a second later when he tells Gerry to remain in his vehicle, he's suddenly mown down by a PWD dump truck even though as he's pulling up there's two lanes of cars and taxis backed up to the end of the street with no dump truck in sight and no way for it to charge through unobstructed.
When the motorcycle hits the side mirror of Gerry's car in the traffic jam, the mirror falls between Gerry's car and the vehicle in front of him. When Gerry picks up the mirror, it is already in the front wheel of his car.
When Gerry and Segen leave the W.H.O center in Wales, Segen is wearing a black hood over her head. In the next scene, immediately after stepping through that gate, Segen's head not covered up by that black hood.
As the passenger plane comes into land at Cardiff Airport the background images show Snowdon and other mountains in the Snowdonia region. It would be highly unlikely that a route from Jerusalem to South Wales would take them to North Wales.
When they are done refueling the plane in Korea, the navy seal pulls the hose off like it is a snap on, when in actuality it is a D-1 nozzle which has a lock that has to be turned and then the nozzle itself has to be turned counter clockwise before being taken off.
When the grenade detonates in the Airbus, the plane suffers decompression and the pilots' oxygen masks drop, yet the aircraft is flying low (circa 3,000 feet) where the pressure would be equal inside and outside the aircraft so that the oxygen masks would not drop.
On passenger aircraft such as the Airbus A310 the protagonist boards in Jerusalem, ladders do not automatically extend from access hatches. The hatches have to be opened (and the ladders lowered) manually.
The helicopter that extracts the family from the Newark rooftop is an HH-65 Dauphin. The U.S. Navy doesn't operate any HH-65 Dauphin helicopters. The U.S. Coast Guard is the only branch of the U.S. military to do so.
During the movie's opening action sequence, British-style traffic lights can be seen at the road junctions, behind the US-style traffic lights, giving away the fact that this scene was filmed in Glasgow, Scotland.
When the Lane family's Volvo is hit by the ambulance at the beginning of the movie, the car is then shown from the driver's side. It is clear that there is no one in the Volvo, and the person driving the ambulance is wearing stunt gear, complete with helmet.
The goof item below may give away important plot points.
After the grenade explodes in the plane, the pilots put on blue emergency helmets, equipped with oxygen masks. In the following sequence when they appear, they just wear their standard microphone helmets.