U.S. & World News

PARIS (CBS) ― A Brazilian air force spokesman says more debris from the crashed Air France jet has been spotted. This comes on the heels of a report that the airline received a bomb threat to a flight from Argentina to France.

The new debris includes what appears to be a 23-foot long chunk of the plane. But Col. Jorge Amaral says there were no obvious markings that would identify the jet.

Amaral says no bodies were seen in the latest wreckage spotted about 55 miles south of where the main debris field lies.

Also spotted were about 10 other metal objects and an oil slick stretching about 20 kilometers in the area.

The main debris field lies about 400 miles northeast of the Fernando de Noronha islands off Brazil's northern coast.

News that Air France received a bomb threat to a flight headed from Buenos Aires, Argentina to Paris surfaced, ABC News reported. The threat occurred last week and after a 90-minute search, no explosives were found, ABC News reported.

Earlier, a French accident investigator says it is unclear whether the chief pilot of Air France Flight 447 was at the controls when the plane crashed into the Atlantic Ocean.

The head of France's accident investigation agency, Paul-Louis Arslanian, also says he is "not optimistic" that rescuers will recover the plane's black boxes miles (kilometers) under the water.

Pilots on long-haul flights often take turns at the controls to remain alert. Asked whether the chief pilot was in the cockpit when the plane went down, Arslanian told a news conference in France on Wednesday that there was no confirmed information either way.

He noted "we don't even know the exact time of the accident."

He also told reporters there were no indications of a problem with the plane before it left Rio de Janeiro on Sunday night en route to Paris.

The disappearance of the Air France jet has shed light on a little-known fact about trans-Atlantic flights: once planes are about 150 miles off shore, they are beyond the reach of radar and the pilots are essentially on their own, reports CBS News correspondent Nancy Cordes.

"The techonology is pretty much like World War II," Mary Schiavo, former inspector general for the U.S. Department of Transportation, told CBS' The Early Show.

Brazilian military pilots first spotted the floating debris early Tuesday in two areas about 35 miles apart, said Air Force spokesman Jorge Amaral. The area is not far off the flight path of Flight 447.

Jobim said the main debris field was found near where the initial signs were spotted.

Weather and aviation experts are focusing on the possibility of a collision with a brutal storm that sent winds of 100 mph straight into the airliner's path.

"The airplane was flying at 500 mph northeast and the air is coming at them at 100 mph," said AccuWeather.com senior meteorologist Henry Margusity. "That probably started the process that ended up in some catastrophic failure of the airplane."

Towering Atlantic storms are common this time of year near the equator - an area known as the intertropical convergence zone. "That's where the northeast trade winds meet the southeast trade winds - it's the meeting place of the southern hemisphere and the northern hemisphere's weather," Margusity said.

But several veteran pilots of big airliners said it was extremely unlikely that Flight 447's crew intended to punch through a killer storm.

"Nobody in their right mind would ever go through a thunderstorm," said Tim Meldahl, a captain for a major U.S. airline who has flown internationally for 26 years, including more than 3,000 hours on the same A330 jetliner.

Pilots often work their way through bands of storms, watching for lightning flashing through clouds ahead and maneuvering around them, he said.

"They may have been sitting there thinking we can weave our way through this stuff," Meldahl said. "If they were trying to lace their way in and out of these things, they could have been caught by an updraft."

The same violent weather that might have led to the crash also could impede recovery efforts.

"Anyone who is going there to try to salvage this airplane within the next couple of months will have to deal with these big thunderstorms coming through on an almost daily basis," Margusity said. "You're talking about a monumental salvage effort."

Remotely controlled submersible crafts will have to be used to recover wreckage settling so far beneath the ocean's surface. France dispatched a research ship equipped with unmanned submarines that can explore as deeply as 19,600 feet.

A U.S. Navy P-3C Orion surveillance plane - which can fly low over the ocean for 12 hours at a time and has radar and sonar designed to track submarines underwater - and a French AWACS radar plane are joining the operation.

France also has three military patrol aircraft flying over the central Atlantic, two commercial ships reached the floating debris, and Brazilian navy ships were en route.

Even at great underwater pressure, the black boxes "can survive indefinitely almost," said Bill Voss, president and CEO of the Flight Safety Foundation in Alexandria, Virginia.

"They're very rugged and sophisticated, virtually indestructible."

Voss said he expected the recovery process to go quickly.

"I'm hoping they'll have stuff up in a month, if not just a few weeks," he said.

Rescuers were still scanning a vast sweep of ocean. If no survivors are found, it would be the world's worst civil aviation disaster since the November 2001 crash of an American Airlines jetliner in the New York City borough of Queens that killed 265 people.

(© 2009 CBS Broadcasting Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)