They have been identified as 75-year-old Winton resident Carl Kruppa, 67-year-old Winton resident Nannette Plett-Kruppa, and 32-year-old Santa Cruz resident Stuart Camenson.
RELATED: 3 people killed after planes collide during landing at NorCal airport
The cause of the crash is being investigated by the National Transportation Safety Board and Federal Aviation Administration.
The NTSB said on Friday it could take up to two years for a final report of the investigation to be issued.
The collision happened as the two planes were attempting to land at Watsonville Municipal Airport on Thursday, the Santa Cruz County Sheriff's Office confirmed Friday.
VIDEO: Surveillance footage shows aftermath of deadly Watsonville plane crash
Surveillance video shows aftermath of deadly Watsonville plane crash
The crash was reported around 3 p.m. Thursday involving a single-engine Cessna 152 with one person aboard and a twin-engine Cessna 340 with two people aboard as both planes were on their final approaches to the airport, Federal Aviation Administration spokesperson Ian Gregor said.
EDITOR'S NOTE: The video above is from a previous broadcast and will be updated.