Character mistake: At the memorial service the principal says that it's been 39 days since 39 loved ones had died. But there were 40 students on the plane and 4 chaperones, making the total 44. Now 7 people got off the plane, which means 37 people related to that memorial service actually died, not 39. Two pilots would make up the numbers, but there would be flight crew too, which still leaves the numbers off.
Plot hole: When Alex and Clear are sitting and having coffee they are on a corner. He looks in the window to see the bus pass, and as he looks to see if it is there, it's not. As the camera pans across the street, there is some construction going on which is blocking that whole road from being used, but then Terry, Carter's girlfriend gets "waxed" by the bus - no way it could have got through all that construction.
Factual error: The teens are traveling presumably along the Meadowbrook or Wantagh parkways, when they enter Jones Beach. They see a sign just before the beach entrance that says "New York: 93 miles", when Jones Beach is less than 15 miles from NYC limits and approximately 25-30 miles from Manhattan.
Revealing mistake: You can see the plane intact even though it has exploded. It stays complete, there's just fire around it. (00:18:55)
Continuity mistake: At the end when Clear is in the car, trying to get away, she knocks over a can of turpentine. When you look at the can again it has changed the way in which it fell.
Revealing mistake: In the scene where Carter drives madly down the road to get to Alex, and Billy is riding his bike along the street, just before Billy gets knocked off you can clearly see it is a stunt double.
Other mistake: The scene where Clear is in the garage, she puts the car in drive, but somehow reverses the car through the garage door. (01:24:49)
Factual error: Later in the movie when Mrs. Lewton is playing John Denver's Greatest Hits, there's two things wrong with the scene: Rocky Mountain High plays as track 1, but is not the first track on that album; second, the song is out of order. The line "but the string's already broken, but he doesn't really care" is repeated twice before her death.
Audio problem: The wheels of the police car screech when there's gravel on the street.
Continuity mistake: In the scene where Alex is watching the TV on how the plane exploded, look at the illustration shown. Then compare it with the illustration that appears on Alex's computer screen. The positions of the explosions shown are different. (00:50:42)
Deliberate mistake: When Alex is in the cabin opening the can the pull tab is already lifted up making it easier to open because he is wearing gloves. It was already up when he took the wrapper off.
Continuity mistake: Late in the film, Alex Browning hides out in the cabin and attempts to make it as death-proof as possible, securing everything therein with ropes and duct tape, and carefully placing his kerosene lantern in a tray of water. At first, we see that the antique lantern is painted dark green; but, one scene later, the same antique lantern (in the same tray of water) is now painted bright red.