Plot hole: The whole concept of a kidnapper 'pretending' his victim didn't get on the plane in the first place is utterly laughable. Even if nobody saw her in her seat, why didn't they see her walking down the aisle to her seat, or waiting to board the plane, or in the boarding tunnel itself? Why isn't she listed on the passenger manifest, or on her mother's travel documents or airline ticket? And there would have been security cameras all over the airport.
Continuity mistake: Straight after the second task Hermione wraps her own white towel round Harry, but between shots it jumps back to her shoulders, then back to Harry's several times. (01:35:05)
Revealing mistake: Before Paxton is hit with the 3 prong instrument, you can see the bloody holes already on his shirt. (01:01:20)
Character mistake: When Lisa is taken to the hospital, she tells Kathy that she saw the ghost of Jodie DeFeo. The name of both of the DeFeo's daughters wasn't Jodie. Their names were Dawn and Allison. Jodie was the name of a demonic pig that the Lutz's daughter Missy had befriended.
Suggested correction: While this is true in the original novel, the writers chose to change it to the DeFeo's daughter's name in the movie. Creative license doesn't count as a mistake.
Continuity mistake: When John is driving to work and he hears Anna on the radio, he swerves to avoid a car. From inside the car you can see that there are no cars in the rear window, yet when the shot changes to an outside shot, there are 3 cars. (00:33:35)
Continuity mistake: As Rachel is preparing the peanut butter and jelly sandwiches, she places the knife on top of the open PB jar in a closeup, but in the very next shot the knife has disappeared, then reappears again. (01:23:15)
Continuity mistake: The chain saw on the block of ice switches ice blocks more than once.
Factual error: In the fire at the lighthouse, Stevie puts her hand on the fire extinguisher nozzle. It would have frozen her hand and made it stick to it.
Plot hole: In the end, when Charlie is advancing on Emily while turning his light on and off, the final time he turns it on, Kathrine is in front of Emily. How could she get there so fast without being heard? There's at least 4-5 inches of water that would make sneaking very hard.
Revealing mistake: Towards the end when Harmony calls Perry's phone as she's lying on the ground, Harry grabs the phone and looks at the caller ID to see her name. Unfortunately that's not the display showing who's calling. Anyone who has a Nokia phone will recognise that that's showing the contact list with just two entries - Harmony and a random number. The fact that it says "contacts" at the top of the screen is a bit of a giveaway.
Continuity mistake: When Hal and Catherine are arguing before she goes to the airport, her ponytail switches between going over the front of her shoulder and hanging straight down her back between shots.
Visible crew/equipment: When Betsy is having the sheet pulled up over her, the lightning flashes and lights up the visibility. You can see a wire which is being used to guide the sheet.
Revealing mistake: When Gretchen turns around while on the bed, a shard of glass in the frame flaps in the wind.
Continuity mistake: After Amy stabs the knife into the table next to the bed, it changes position in following shots.
Factual error: The vehicles in the movie have front and back license plates. The state of Florida does not have front plates, only back.
Plot hole: In the course of the story it's said that at the time the black hole went out of control, it had a mass of "half a mountaintop of granite." But in a flashback scene Dr. Krone is shown growing the mass of the hole by feeding it large numbers of lead bricks in the laboratory. It's a little hard to believe his lab could store, or even afford, enough lead bricks to equal that much mass.
Continuity mistake: When Granny uses her solo ski as a snowboard the ski becomes much bigger on its own.
Visible crew/equipment: When Brendan is talking to V.P. Trueman, a boom microphone is seen moving in the reflection of a picture frame to the left of Trueman.
Continuity mistake: After Dan is injured a bandage is placed horizontally above Dan's left eye. In all subsequent shots and scenes the bandage is at an angle.
Continuity mistake: When Tim goes to the house and Kate falls off her horse, they go inside. When she leaves you can hear a car engine start. If she rode her horse to the house how did she get her car there?