Federal Aviation Administration spokesman Ian Gregor says the six-seat Beechcraft Bonanza and the two-seat Robinson R22 helicopter collided Sunday near the small Rio Vista Municipal Airport 50 miles northeast of Oakland.
No specifics on the crash were released.
Gregor says the helicopter landed in a field about eight miles south of the airport, and the plane went down short of the Byron Airport where it was trying to land 20 miles to the south.
Gregor says there are no reports of injuries on either the plane or the helicopter, and the helicopter pilot refused medical treatment.
It's not clear how many people were aboard the two aircraft.