Military aircraft and ships searched the ocean off Southern California for any sign of the victims while investigators gathered recordings of air traffic controllers and pilot communications. The search covered 644 square miles of ocean but focused on a debris field 50 miles off the San Diego coast.
The crash involved a Coast Guard C-130 with a seven-member crew and a Marine Corps AH-1W Super Cobra with two aboard as it flew in formation near the Navy's San Clemente Island, a site with training ranges for amphibious, air, surface and undersea warfare. It was not known whether the pilots were aware of each other before the 7:10 p.m. Thursday collision.
"A tragic event," Pentagon spokesman Bryan Whitman said. "The search is still on, but it's likely taken the lives of nine individuals."
In San Diego, crews of Navy ships, Coast Guard cutters and helicopters planned to keep scouring the ocean even though nearly a full day had passed since the accident.
"We're still in the search-and-rescue phase, we are not standing down from that at this point," said Capt. Tom Farris, commander of the Coast Guard's San Diego sector. "We have every hope we will find survivors.
The identities of the crew members were not immediately known. The C-130 crew had survival gear aboard the aircraft, including exposure suits that could have allowed them to survive in the water for hours, Petty Officer Henry Dunphy said.
The Sacramento-based C-130 crew was looking for a man on 12-foot motorized skiff who was reported missing after leaving Avalon Harbor on Santa Catalina Island to reach a friend on a disabled yacht that had gone adrift off Catalina in high winds Tuesday, authorities said.
The Marine helicopter was flying from Camp Pendleton near San Diego to San Clemente Island, said Maj. Jay Delarosa, a spokesman for Marine Corps Air Station Miramar in San Diego.
Two Super Cobras, a type of attack helicopter, were escorting two big CH-53E Super Stallion transport helicopters carrying Marines to the island, Delarosa said. He did not know how many Marines were aboard the transports.
After the collision, the other three helicopters returned to base, he said.
The accident occurred in airspace uncontrolled by the FAA and inside a so-called military warning area, which is at times open to civilian aircraft and at times closed for military use, said Federal Aviation Administration spokesman Ian Gregor. He added that he did not know the status of the airspace at the time.
Minutes before the collision, the FAA told the C-130 pilot to begin communicating with military controllers at Naval Air Station North Island in San Diego Bay, but it was not known if the pilot did so, Gregor said.
FAA controllers never communicated with the Cobra pilots, Gregor said.
Farris, the Coast Guard commander, said it is not unusual to have a high volume of military traffic working in training areas. "That's not unusual," he said. "We do that every night and it's something we're trained to deal with."
He said pilots in the area are responsible for seeing other's aircraft around them.
Pilots "operate in that area on a see-and-avoid principal," he said.
Farris said experts on operations, maintenance and safety arrived in San Diego on Friday to begin collecting evidence to produce a report on the cause of the collision to prevent another accident.
The investigation will involve recordings of transmissions by the aircraft, the FAA and Navy controllers, he said.
The four-engine C-130 was conducting its search from an altitude of 900 to 1,000 feet and visibility was 15 miles, according to the Coast Guard.
Citing the continuing investigation, Delarosa said he couldn't comment on whether the helicopter pilots were aware of the Coast Guard search operation. He said that since it was after dark, the helicopter pilots would have been wearing night-vision goggles.
The aviation division for Camp Pendleton and Miramar suspended flights through the weekend, Delarosa said. Incoming aircraft will be allowed to land at the bases.
Navy spokeswoman Angelic Dolan declined to answer questions about the collision.
The search for the man on the skiff continued.
He was identified as David Jines, 50, a resident of Catalina, said Los Angeles County Sheriff's Lt. Jeff Donahue.
Jines left Avalon around 8 p.m. Tuesday on a skiff to go help a friend, Linda Jones, who was having trouble keeping her 57-foot vessel anchored in high winds, Donahue said.
Jones told The Associated Press that Jines boarded her yacht and helped her maneuver to a quarry where they thought they had made anchor.
"He thought I was safe so he decided to go back home," Jones said. "I said, 'I don't think you should go.' But he said he had to get back to his sailboat." She said Jines' sailboat was anchored at the Avalon harbor.
She said the anchor didn't hold and a Coast Guard cutter ultimately towed her boat to Los Angeles. She reported Jines missing the next day when she returned to the harbor and couldn't find him.
"I didn't know Dave was in any kind of peril," she said.
The C-130 was based at the Coast Guard's air station in Sacramento.
Coast Guard flotilla Cmdr. Ron Clark said the primary mission of the base's C-130s is search and rescue in an area stretching from the Canadian border to Ecuador and halfway to Hawaii. The station is also responsible for marine enforcement ranging from drug interdiction to fisheries.
Clark declined to discuss the collision, referring calls on that to the San Diego operations.
A C-130 from Hawaii was flown to Sacramento on Friday to allow the station to continue operating normally.
The offshore military airspace occupies a wide swath of area from the U.S.-Mexico border to California's central coast.
Military flights are common along the San Diego County coast. Marine helicopters are often seen flying from coastal Camp Pendleton to ships and the island.
Nguyen reported from Los Angeles; Associated Press Writer Juliet Williams in Sacramento contributed to this report.