Two planes linked to a Miami flight school crashed midair over the Florida Everglades.
Police confirmed three people were killed in the crash, and are investigating the possibility that a fourth person was killed.
Identities have not yet been released.
The crash happened around 1pm local time (6pm BST) on Tuesday, about nine miles west of Miami Executive Airport.
The collision involved a Piper PA-34 and a Cessna 172.
The planes both belonged to Dean International flight school.
It is thought they were being flown by trainers.