(CNN) -- Rescuers were still searching Saturday for nine people missing in the Pacific off the southern California coast after a Coast Guard C-130 plane and a Marine AH-1 Cobra helicopter collided Thursday night.
"We will continue to search however long, hope -- however slim -- exists," U.S. Coast Guard Rear Adm. Joseph Castillo said Saturday.
But Castillo said, "The reality is that as time goes by, and our extensive searches do not yield success, that our hope today is not what it was yesterday."
He said a decision on the next course of action would be made Sunday.
Marine Corps Air Station Miramar identified the Marine pilots of the AH-1W Super Cobra as Maj. Samuel Leigh and 1st Lt. Thomas Claiborne, both with Marine Light Attack Helicopter Squadron 469.
They were conducting routine training about 15 miles off San Clemente Island when they collided with the U.S. Coast Guard C-130.
The Coast Guard identified its seven missing personnel as Lt. Cmdr. Che J. Barnes of Capay, California, aircraft commander; Lt. Adam W. Bryant of Crewe, Virginia, co-pilot; Chief Petty Officer John F. Seidman of Stockton, California, flight engineer; Petty Officer 2nd Class Carl P. Grigonis of Mayfield Heights, Ohio, navigator; Petty Officer 2nd Class Monica L. Beacham of Decaturville, Tennessee, radio operator; Petty Officer 2nd Class Jason S. Moletzsky of Norristown, Pennsylvania, air crew; Petty Officer 3rd Class Danny R. Kreder II of Elm Mott, Texas, drop master.
They are stationed at Coast Guard Air Station Sacramento, California, where their aircraft is based.
A pilot reported seeing a fireball about 7:10 p.m. Thursday near the crash site.
The search and rescue mission has covered an area of 644 square miles, and has included Coast Guard, Navy, Marine Corps and Customs Border Protection assets, the Coast Guard said.
U.S. Coast Guard Rear Adm. Joseph Castillo said Friday that an investigation with the Marine Corps to determine what happened was beginning.
A large debris field has been located, and debris has been collected, he said. The two Marines on the Marine Corps Base Camp Pendleton chopper were one of four helicopter crews involved in the training exercise.
The Coast Guard plane had been on a search mission for a couple of days before Thursday's crash.
"They were searching for a possible person in the water who was reported to have gotten in a dinghy and attempted to row to Catalina [Island]," Coast Guard Capt. Thomas Farris told reporters Friday. "We were searching in that area because of the drift that would have naturally occurred after that event."
With water temperatures in the 60s, Farris estimated that survivability could be up to 20 hours.
The missing person the Coast Guard members were searching for is still missing, Farris said.