Factual error: The vehicles in the movie have front and back license plates. The state of Florida does not have front plates, only back.
Other mistake: The exact same background shot of a Ventura bomber followed by two single-engine planes flying left to right is used three times during the film, twice at the beginning as they are planning the mission on the beach and then once at the end when the raid is over.
Continuity mistake: When Johnny is walking out of the dirt bike stadium, he has his arms around two women's shoulders. The shot changes, now the two women are holding on to his arms. The shot changes again, and now his arms are free. It happens too fast for him to just let go of the women. (01:00:35)
Continuity mistake: The name on Travis' helmet switches between 'Ryer' to 'Travis' several times throughout the movie.
Revealing mistake: During the shoot out with McGivens's gang at the Cortez ranch, the wife of Cortez sneaks out of the trap door with her baby and peers around the side of the building. You can notice that the baby is really a doll.
Other mistake: Michelle Rodriguez's accent changes several times, not only throughout the movie, but sometimes within the same scene.
Continuity mistake: Just after Tom has finished making love to his wife on the stairs we see him lying there with his left arm across his groin area. When the shot changes, his arm has moved up crossing his chest. (01:06:55)
Factual error: In the first scene at the Pentagon, the sergeant tells the other officer that all satellites are being put into geosynchronous orbit to "hide them behind the planet." But objects in geosynchronous orbit don't remain hidden behind the Earth relative to the sun; they orbit once a day, remaining over a particular longitude on earth. Therefore, they would be subjected to the magnetic storms every day, during daylight at that longitude.
Factual error: In order to be electrocuted you need to connect a high voltage to a low voltage. Touching a power line does not get you electrocuted unless you make contact with the ground. So electrocuting the locusts by making them fly against a powerline can not work because they are not 'grounded'.
Plot hole: The survivors find their way to the internet lounge to send out a message via email about the terrorist attack. The ship was upside down. All satellite dishes used to transmit over the internet were completely submerged in water. Even if there was power to the computers, they would not have been able to get a server connection let alone send out email.
Continuity mistake: When Vann and Andy are at eating burgers, Vann is seen drinking from his cup in some angles and in others the cup is in resting in his hand.
Audio problem: Just after the long continuous fight scene in the restaurant, one girl pulls out a knife to attack Tony Jaa. The knife makes a sound like it's being pulled from a sheath but it's not touching any other metal.
Continuity mistake: During the song sequence of "Chham Se Woh A Jaye"(the wedding song), Abhishek Bachchan's dupatta keeps changing the way it is wound around. Once it is around his left shoulder, and once around his right. This continues throughout the song, whenever the camera focuses on him and Zayed Khan.
Continuity mistake: When the cast is at the night pep rally, as Tommy Lee Jones is giving his speech to the student body, his candle keeps changing lengths. (01:18:00 - 01:20:00)
Continuity mistake: In the scene at the end of the film when the Z-Boys finally get to skate in Sid's empty pool, the skateboard that is left on the steps changes position every other shot. When the guys first get into the pool, it is facing board-side out. In the next shot, it is facing wheel-side out. Then it alternates back and forth until the end of the scene.
Revealing mistake: Quite obviously Steven Seagal is not jumping out of the warehouse window himself, it's blatantly a stuntman.
Continuity mistake: In this scene we see the police car chasing Wesley Snipes' car. During the chase we see that Snipes' car has sustained heavy damage to both front doors, then when the car finally comes to a stop after the chase, it has repaired itself. The doors are repaired with only slight damage to the right front.
Continuity mistake: When Beowulf enters the water cave and seeing Grendel's body, the initial shot has his right arm sitting next to him (most likely placed there after his mother's took it from the Meat Hall). When Beowulf leans over to touch Grendel's chest, the arm is gone.
Visible crew/equipment: Near the end, when the monster has crashed through the wall of the bar, the monster rips off his deer skull mask/helmet to show his true face. As soon as he tears the mask/helmet away, look carefully to the right of the screen. For a split second, you can see the black outline of a person standing beside it. (This is revealed in the commentary.)
Other mistake: After the Joker has become a vampire, you can still see his reflection in metal poles and such while he is chasing Batman in the bloodbank. (00:47:00 - 00:49:00)