Authorities say two small planes collided and then crashed in the desert near Milepost 7 and New River Road, killing all four people aboard the two aircraft.
Phoenix and Daisy Mountain Fire Department officials said the collision and crash involved two single-engine planes with two people in each aircraft around 10 a.m. Friday, about 15 miles northwest of Deer Valley Airport.
There were no survivors.
Several bystanders reported seeing the planes collide but the flight directions of the planes before the crash or other details weren't immediately available, officials said.
"Both of them collided. We don't know how or what," said Phoenix Fire Department Capt. Larry Nunez. "The skies are clear."
Only the charred wreckage left from one of the planes could be seen, while the other was fairly intact.
The intact plane was a Piper Archer III, manufactured in 2002 and owned by Bird Acquisition, LLC, which does business as TransPac Aviation Academy, a school for commercial pilots in north Phoenix.
Two of the dead were instructors at the school, according to a statement by TransPac.
The second plane, which sustained significant damage, was a Cessna. The
plane is part of WestWind School of Aeronautics.
Federal Aviation Administration spokesman Ian Gregor says the National Transportation Safety Board and the FAA will investigate. It could take months before the cause is determined, Gregor said.
The names of the deceased have not been released.
Video: FOX 10's Ty Brennan reports.
The Associated Press contributed to this report.