Revealing mistake: When Harry tells Marv to go back while they are climbing across the rope, in the shot facing them front-on, you can see Kevin in the background about to cut the rope. If you look closely this is not Kevin, it is his stand-in.
Revealing mistake: Towards the end when Harry walks up the frozen stairs, you can see it switches to a stuntman when he slips and lands on his back. (01:17:55)
Chosen answer: They did but the power and phone lines were down due to a tree branch that had fallen on them the night before the family left. A flight attendant on their plane mentions that attempts had been made to call the McAllisters' home but "the phones are still out of order".
Jeff Swanson
But how did he call the police at the end if the phone lines were down.
That was several days later. Clearly the phone lines were repaired over the course of the film.
The film takes place over 3 or 4 days.
Ssiscool ★
After the storm the lineman tells them the power has been restored but the phone lines are "a mess" and that it would take several days to get them fixed. They were out initially, and then in various stages of repair afterward.
Also explains calling for a pizza.
Ssiscool ★
It's ridiculous though that the phones are apparently working by the time they land (Kate's SIL calls everyone on their street). Yet none of them try the house again.