SAN DIEGO (AP) _ Two Navy submarine-hunting planes collided Thursday, and all 27 people aboard were feared dead in cold, choppy waters 60 miles off Southern California, authorities said.

The Navy listed the crews as missing but there was little hope any of the crew members from the downed P-3 Orions survived.

The all-weather planes were engaged in an anti-submarine warfare training exercise when they collided in bad weather, authorities said.

''I think we have to be realistic here,'' said Senior Chief Petty Officer Bob Howard, a Navy public affairs officer at North Island Naval Air Station. ''It is very cold out there. We're talking about what apparently is a mid- air collision ... two aircraft. I would say it would be very grim.''

Still, he said, the Navy was conducting an aggressive air and sea search of the crash site.

Search and rescue teams spotted and retrieved some debris from the planes but found no signs of life. Further details about what was found were not immediately available, Howard said.

There was no word on how long the search would last, but Howard said the Navy would make ''extraordinary'' attempts to retrieve remains and wreckage.

A Navy helicopter crew flying in the area and sailors from the destroyer USS Merrill all reported a ball of fire and loud explosion at about 2:30 a.m. PST, Howard said during a briefing at North Island Naval Air Station.

He said the accident occurred over the Pacific Ocean about 60 miles southwest of San Diego.

''They were operating in conjunction with other surface and air elements when a mid-air explosion was reported approximately the same time radio contact was lost,'' Howard said.

The collision occurred as one P-3 Orion was arriving to relieve the other, which had just completed its part of the exercise, Howard said. Officials were uncertain how much contact the pilots had before the crash, he said.

The aircraft carrier USS Abraham Lincoln, the USS Merrill and at least two other ships, along with helicopters and fixed-wing planes were assisting in the search.

Howard said it was believed 13 crew members were aboard one P-3 Orion and 14 on the other. The planes were on a training mission from Moffett Naval Air Station near San Jose. Names of crew members were withheld pending notification of their families.

''It's just not a good feeling right now at Moffet Field,'' said flyer Joe Askin. About 5,500 military personnel are stationed at Moffet.

Tina Krohn, a waitress at a nearby restaurant frequented by military personnel whose husband is a pilot stationed at Moffet, said the tragedy reminded her of the risks of his job.

''I'm scared for him every day,'' she said. ''I'm scared enough thinking about everyone now.''

The P-3s were in contact with land- and sea-based air controllers during the exercise, but officials were uncertain who was directing them at the time of the collision, Howard said.

He called that ''a very pivotal point,'' and said investigators will examine how the two planes wound up on a collision course.

''That's obviously something we're looking at,'' Howard said. ''When you conduct an investigation like this, the one thing you don't want to do is rule anything out.''

Showers and strong winds were reported in the San Diego area overnight. About three hours after the planes collided, a funnel cloud was sighted about 5 miles offshore from San Diego's Mission Beach.

The National Weather Service said pilots in the area reported severe turbulence. Howard said the Navy was uncertain what part, if any, weather played in the collision.

The P-3 Orion, driven by four propellers, is regularly used by weather forecasters to fly into hurricanes.

''It is very sturdy and traditionally has been one of the safest aircraft the Navy flies,'' Howard said. ''They have historically proven themselves capable of operating even in bad weather conditions.''

''I've got 21 years in the Navy and this is the first time I've heard of a mid-air collision between P-3s.''

When used to hunt submarines, the planes can be armed with torpedoes, nuclear or conventional depth charges, mines and Harpoon and Sidewinder missiles.

The planes, originally built in 1959 by Lockheed for the Navy, have a wing span of about 100 feet, a length of 116 feet, 10 inches, and a height of more than 33 feet. Their maximum speed is 473 mph, and they have a cruising speed of 378 mph.

Pentagon spokesman Pete Williams said he believed this was the first collision in the air involving P-3s. The Navy has about 300 P-3s.