The incident was reported at 2:11 p.m. on a property in a wooded area in the 17800 block of S. Mountain Road, just outside the city limits of Santa Paula, Ventura County fire officials said.
Ian Gregor, a Federal Aviation Administration spokesman, said the single-engine, homebuilt Vans RV6A crashed under unknown circumstances and caught fire after crashing.
The deceased, a male pilot and a male passenger, were not immediately identified. No one on the ground was injured, officials said.
It was unclear where the plane was coming from or where it was headed, though the crash site was less than a mile from Santa Paula Airport.
Witness Lisa Darling-Daniel said the plane spiraled sideways before it crashed.
"The plane was flying by and I was like, 'Oh, look, the plane is going to do some tricks for you,' and she said, 'That's not a trick,' and then there was a kaboom, and so we all just jumped up and yelled for my son, who's a firefighter, and we all ran across the street to see if we could help," she said.
Ventura County Sheriff's Department Sgt. Eric Buschow said the crash came close to a man on the ground.
"There was a gentleman on this property behind me spraying some plants with a portable sprayer, and he heard the plane coming in, looked up, saw it going north to south at a very low altitude, and he literally put his sprayer down and ran, and where his sprayer ended up to where the wreckage is now on the plane is probably about 50 feet," Buschow said.
The crash will be investigated by the FAA and the National Transportation Safety Board.