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.
Factual error: The teens are traveling presumably along the Meadowbrook or Wantaugh parkways, when the 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.
Continuity mistake: Right before Terry is hit by the bus, there are puddles and wet patches all over the road and path. But when the bus actually makes contact with Terry, they all instantly disappear. On top of that, during the kid's conversation before Terry gets hit by the bus, you can see that when the bus comes from the left, it is forced to turn right. This means there isn't enough space and time to gain the speed at which it hits Terry. (00:47:10)
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.
Continuity mistake: When Ms. Lewton dies, she is grabbing her bleeding neck with her left hand. While walking into the kitchen, she leans onto the kitchen table with her right hand. Later in the scene, when Alex comes and tries to help her, we see the bloody left hand impression on the table, even though we should see the right one.
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.
Trivia: The filmmakers originally had an ending in which Alex grabs the cable that lies on Clear's car, Alex catches fire and dies. Then Clear gets her baby and Carter survives. The test audience didn't like this, so the filmmakers shot another ending in which Alex is decapitated by a crashing police helicopter. But again, the test audience didn't like the fact that Alex dies, so they shot the finish with the billboard, which took 6 days to film and cost nearly $2,000,000.