Carrie/WMG

Carrie caused the crash of Oceanic Flight 815.
Note: the following is based on the remake.

Chris somehow survived after Carrie threw the truck she was in against a tree. Afterward, she changed her name to Claire Littleton and moved to Australia. Carrie found out that her old nemesis was still alive, and followed her down under to kill her. When Chris/Claire got on the flight to Los Angeles, Carrie stowed away in the cargo area and tried to wait until the plane was out over the open ocean so that she could get her revenge. Unfortunately, the EMP from Desmond's missing of the button caused Carrie's powers to go berserk, bringing the plane down early and in the South Pacific, which is filled with desert islands that a plane can (semi-)safely land on.

The reason there were survivors at all, then, would be that Carrie, as the plane was going down, instinctively used her telekinesis to buffer the crash-landing. She never shows up on the island because she was in the cargo area, and, still reeling from the misfire of her powers, was crushed by the plane.

Carrie doesn't go to Florida at the end of The Remake. She goes to New York.
While there, she hears about a school in Westchester run by a man with a history of helping people like her.