'Fireball' Off California: Coast Guard Plane, Navy Chopper Collide

Oct. 30, 2009— -- The search continues for nine military personnel missing after a mid-air collision of two aircraft off the southern California coast Thursday night. So far, rescuers have not found any survivors or remains.

Officials say a Coast Guard C-130 transport plane, which carried seven passengers, had been on a search and rescue mission for a small boat reported missing since Wednesday. The U.S. Marine Super Cobra AH-1W helicopter, manned by two aviators, was conducting a training exercise out of Camp Pendleton.

Shortly after 7 p.m. Thursday night, an eyewitness reported seeing two large explosions and a large fireball 50 miles off the San Diego coast and 15 miles east of San Clemente Island.

Watch Lisa Stark's report on the latest developments tonight on World News with Charles Gibson at 6:30 p.m. ET.

The Coast Guard told ABC News that the weather was clear at the time of the accident and search conditions remain very good.

"Throughout the night the U.S. Coast Guard and the U.S. Navy have actively engaged in the search for survivors. There is a debris field that has been located, and we're continuing to search for survivors," said a U.S. Coast Guard spokeswoman, Petty Officer Second Class Jetta Disco.

The Coast Guard says the window of survivability for the nine personnel is 20 hours or more in the ocean waters, depending on their body type and the equipment they may have worn.

"We are always hopeful. We're working hard. And the assumption is always that they are alive," said Capt. Tom Farris, commander of the Coast Guard's San Diego sector, at a press conference this morning.

ABC News has been told the mid-air collision could have been much worse. Marine spokesman Major Jay Delarosa said the helicopter involved in the collision was flying in formation with three other helicopters at the time of the collision -- one other AH1-W and two CH-53s. The Cobras were flying escort for the CH-53s.

Investigators will likely focus on communications between the pilots and air traffic controllers, since early reports suggest there were not problems with the aircraft themselves.

Crash Investigators Likely to Focus on Communications

The FAA said its controllers were in contact with the C-130 until several minutes before the crash, when they told the pilots to contact military air traffic control. The plane was about 1,000 feet over the ocean at the time, entering airspace used for military exercises. FAA spokesman Ian Gregor said he did not know if the pilots ever talked to military controllers.

Lt. Cmdr. Chris O'Neil of the U.S. Coast Guard tells ABC News that military situation reports indicate that the C-130 was in contact with military controllers, but he couldn't confirm that from first-hand knowledge.

O'Neil said investigators are unsure whether the crew of the C-130 was using night vision goggles during the flight. The aircract has other sensor systems that can be used at night for search and rescue without the crew resorting to night vision goggles, he said.

If the helicopters and C-130 were operating in a military exercise area, it would have been up to the pilots and crew to "see and avoid" each other. Air traffic control and radar tracking would have provided awareness of other aircraft in the area, but as one pilot told ABC News, "When you're in those areas it is the wild west."

The search for debris and survivors continued Friday, both on the water and from the air.

"We've had three to four helicopters search all night long," Rear Admiral Joseph Castillo told ABC News. "Basically, we have a search area that's 644 square miles that is the area of primary concentration."

Five Coast Guard cutters and four Navy surface vessels are also participating in the search and rescue operation.

Coast Guard commander Farris said the families of all nine personnel have been notified.

This morning at a building dedication, Homeland Security Secretary Janet Napolitano briefly spoke about the crash.

"All of us are thinking of our Coast Guard and Marines colleagues," Napolitano said. "There are extensive efforts going on to see if there are survivors." She then asked for a moment of silence.

ABC News' Martha Raddatz, Luis Martinez and Jason Ryan contributed to this report.