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.
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.
Continuity mistake: The scene where Clear is in the garage, she puts the car in drive, but somehow reverses the car through the garage door.
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.
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.
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: 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.
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.
Factual error: The flight attendants didn't do the safety briefing properly. None of the flight attendants show the demonstrations. Also, the safety briefing should be given during taxiing to the runway. But in the movie, the flight attendant had finished the safety briefing before the door of the plane closed. During the safety briefing, the flight attendant said that the aircraft has 6 emergency exits. How come a 747 has only 6 exits? A 747 in fact has 5 main deck exits on each side, which means on the main deck there are 10 exits. Judging by the picture of the plane on the DVD inner cover (New Line Platinum Series), the 747 used in the movie most likely is the 747-200 series, which means the upper deck has one emergency exits. All in makes the plane has 11 exits, almost double the number said by the flight attendant. And during the take off, when Alex looks outside the plane to the wing, he sees that the flaps are just being deployed. When a plane is taking off, the pilot needs to make sure that the flaps are deployed BEFORE they are actually on the runway.
Other mistake: When the plane takes off in Alex's vision, the plane begins to go into a nosedive, and the entire left fuselage is blown apart, sucking many people out of the plane. The plane then explodes completely, but in reality, the plane just takes off, and explodes almost instantly afterwards. No struggling with the plane is shown in reality, nor is the plane going into a nosedive. This is also proven in FD5, which is a prequel. The jet engine explodes, leaving a flaming tail, and the plane spinning out of control. The plane just simply "explodes" without any signs of struggle.
Continuity mistake: When you see Alex watching the news report about the crash of 180, after coming back from the airport, you see his mum and dad asleep on the couch with a pillow at the end of his mothers foot and a few shots later after hearing the loud thunder, the pillow is lying on her ankles.
Revealing mistake: When Alex is running through the woods and is sliding down the hill, just before he stops himself from being impaled by some branches, you can hear someway say "Look out." It can't be the agents following as they're too far away.