Two small planes collided over rugged backcountry near McLellan-Palomar Airport in Carlsbad on Tuesday afternoon, killing the pilot in one plane and an instructor and a student pilot in the other.
The identities of the victims were withheld pending notification of relatives.
Officials said the pilots were men and the student was a woman.
The planes, a single-engine Mooney M20E and a twin-engine Beechcraft Duchess, were in the airport's arrival-and-departure pattern when the collision occurred.
Although pilots in the pattern are required to be in radio contact with the airport, it is their responsibility to "see and avoid" other aircraft.
The registered owner of the Mooney is a pilot with a residence in Auburn, Calif. The registered owner of the Beechcraft is Pinnacle Aviation Academy, a flight school at the airport.
George McJimsey, president of the flight school, said the student pilot and her instructor had taken off from the airport, heading west, about 1 p.m. McJimsey said the Beechcraft made a U-turn to the right and was heading east in the pattern, parallel to the runway, when it collided with the Mooney, which apparently was entering the pattern in preparation for landing.
The planes were about 1,200 feet above ground when they collided over an unpopulated area. One plane fell into a ravine near a real estate development site being graded about a mile northeast of the airport. The other came down on a hillside several hundred yards from the ravine. Although both planes were crushed by the impact, neither caught fire.
The Carlsbad Police Department said the bodies were found in the wreckage.