ABC News has confirmed that Air France received a bomb threat

The flight from Rio de Janeiro to Paris vanished with 228 people onboard Sunday night. On Tuesday searchers found debris from the plane floating in the Atlantic 700 miles off the coast of Brazil.

Also today, ABC News has confirmed that Air France received a bomb threat over the phone concerning a flight from Buenos Aires, Argentina, to Paris days before Air France flight 447 disappeared over the Atlantic Ocean Sunday night.

Authorities at Buenos Aires’ Ezeiza Airport delayed the May 27 flight before takeoff and conducted a 90-minute search of the threatened aircraft. Passengers were not evacuated during the search, which yielded no explosive material. After the inspection, authorities allowed the plane to take off for Paris.

Four days later, flight 447 departed from Rio de Janeiro. There was no known threat against the missing flight.

Earlier today, Amaral told reporters the debris is spread out in two main areas, about 35 miles apart, located some 400 miles from the Brazilian islands of Fernando de Noronha. Searchers have seen an oil slick and scattered pieces of debris, including what appears to be a seat, on the ocean.

But bad weather is hampering recovery efforts, with sea currents said to be impeding the process. And weather aside, recovering debris in this part of the ocean may not be easy. The underwater area where the search is focused is extremely mountainous terrain, and Google Earth estimates the water there to be 13,000 feet deep.

"That’s like searching for an airplane in the surface of the mountains. You could be very close and not be able to see the wreckage," said John Hansman, a professor of aeronautics and astronautics at the Massachusetts Institute of Technology.

Still, Brazil’s president, Luiz Inácio Lula da Silva, expressed his determination to find the plane.

"A country that could find oil in 3,700 meters deep in the ocean is going to be able to find a plane 1,200 meters deep," he said in a statement.

Passenger Arthur Coakley’s wife keeps trying his cell phone — also determined to get an answer.

"I haven’t tried it today, but yesterday it was ringing," said Patricia Coakley. "So maybe they’re not at the bottom of the sea."

Today, the head of France’s accident investigation agency, Paul-Louis Arslanian, described the case of the missing flight 447 as the "worst French aviation disaster in history."

Air France Flight 447: Searching for Clues

Arslanian added that France has four groups of investigators working on the case. The first group will search for debris, and the other three groups will study the plane’s equipment and maintenance records. He emphasized that there were no suggestions of any problems with the plane before takeoff.

He also said he was "not optimistic" of recovering the aircraft’s black boxes (cockpit voice and data recorders), which are believed to be buried under the sea.

If found, the plane’s black boxes would provide many more clues about what happened. Experts said the black boxes emit pinging signals, although only for a finite period of time, in the water. With tracking beacons that activate when the boxes get wet, the black box radio signal works for about 30 days. But it won’t be easy for search teams to pick up the signal and find a black box — the size of the proverbial bread box — in rocky terrain.

"It can be done, but I think we’re gonna have to look for a little luck on this too," ABC News aviation consultant John Nance said today.

"They’ll drop those microphones down quite a ways," Nance added.

Lt. Col. Jed Hudson, a commander at Tyndall Air Force Base in Florida, said that all planes also have emergency transmitters in their tails that are designed to send out distress signals in case of emergency.

It’s possible that this one either malfunctioned or there wasn’t a satellite passing overhead to detect the signal at the time the plane was in trouble, he said. The information can be stored and detected once satellites pass overhead — unless it is too far underwater.

No distress calls were made by the crew, but a series of automatic messages was sent by the plane’s system just before it vanished, reporting lost cabin pressure and electrical failure. Arslanian said the messages were received in a time frame of three minutes. Investigators were working to interpret these messages, he added, saying that he did not want to go into details at such an early stage of the probe.

Today, 12 military planes, including one American plane and one French aircraft, and ships were engaged in an operation to recover the debris. A forensic scientist is also believed to be onboard one of the planes to help with the recovery operation.

A French search and exploration ship is also on its way to the crash site. It is equipped with tools to help recover debris, including robots that can plunge about 20,000 feet underwater. It could be a few days before the ship arrives where the debris has been spotted.

"Because of the way this airplane disappeared, we have very little evidence to start to put together what happened," Hansman said. "So anything they can get from the debris field in the ocean is going to be important in terms of clues."

Weather Worries

The reasons behind the crash remain unclear, with many speculating that it could have been a result of thunderstorms and lightning or a combination of both. But ABC News has confirmed that two commercial planes flew virtually the same route as that taken by the Air France jet just before and after the missing flight.

Arslanian said that to the best of his knowledge, the pilot at the controls told Brazilian air control that he was experiencing turbulence about 30 minutes before the plane’s disappearance. He said it was unclear whether the chief pilot was in the cockpit when the plane went down, since pilots usually take turns at the controls during long-haul flights.

He stressed that the investigation was only in its early stages, and he could not confirm how the plane went down.

"We don’t even know the exact time of the accident," he said, adding that "our objective today is to publish the first report by the end of June."

A Lufthansa spokesman told ABC News he knew of one flight in the area at the time, but it is not clear if that plane encountered any poor weather.

"This flight operated normally without any irregularities reported by the crew," Lufthansa said in a Tuesday statement.

French Transport Minister Jean-Louis Borloo said Tuesday he did not believe bad weather alone could have brought the plane down. He also brushed off the idea that terrorism or a hijacking could be involved.

"There really had to be a succession of extraordinary events to be able to explain this situation," he told France’s RTV radio.

Nance agreed that it would be almost unheard of for a plane to be downed by lightning alone but added, "You never say never."

Nance also said Tuesday it’s unlikely that turbulence could break up a plane: "In most circumstances, absolutely not," he said. "The aircraft can take anything the atmosphere can throw at it, except for tornadoes."

In very rare cases, Nance said, a plane could be trying to recover from severe turbulence and then hit more, causing too much stress for the plane.

AccuWeather’s Ken Reeves said towering thunderstorms are common over that area of the Atlantic. He said planes typically fly at about 35,000 to 37,000 feet, and storms in the tropics can be as high as 50,000 feet.

"In that part of the tropics, with as high as the thunderstorms are, it can be difficult having to go hundreds and hundreds of miles out of your way in order to just get to the point you’re trying to get to," Reeves said.

"We are really talking about extreme circumstances here," said William Voss, president and CEO of Flight Safety Foundation. "And so a rainy night out of LaGuardia isn’t what we are talking about. We are talking about situations that are very extreme, very severe turbulence is assumed to have occurred here. And there’s not many of us — not even many pilots that have really experienced severe turbulence. You would know it if you had."

The four-year-old Airbus jet did have sophisticated radar that should have helped the pilots try to skirt any violent weather.

The missing Airbus A330 had 216 passengers and 12 crew onboard when it took off Sunday night. All 12 crew members were French, according to the airline.

The list of the missing indicates a virtual United Nations of passengers. The passengers came from more than 30 countries, and included Americans Michael and Ann Harris, who had been living in Rio for more than a year. Tuesday afternoon, U.S. State department officials said a third American, a dual citizen traveling under a foreign passport, was also onboard.

In addition to the three U.S. citizens, the passengers included 61 French citizens, 58 Brazilians, 26 Germans, nine Chinese and nine Italians. The group included seven children, a baby, 126 men and 82 women.

Michael Harris, a geologist working in Brazil for natural gas and oil producer Devon Energy, had been transferred from Houston to Brazil in 2008.

"We are extremely saddened by this development and trying to monitor the situation as it unfolds," said Devon Energy spokesman Tony Thornton in a statement. "We’re doing what we can to help the family at this time."

U.S. State Department spokesman Robert Wood has said the U.S. government is also in touch with the families of the Americans onboard.

The flight had been expected to land in Paris at 5:15 a.m. ET after leaving Rio around 6 p.m. Sunday night.

The Brazilian air force said in a statement that it had been anticipating radio contact with the plane when it was still over northeast Brazil, but when it received no radio communication, Brazilian air traffic control contacted air traffic control in Dakar, Senegal. There was no mayday call and no nearby planes received a call for help on the international emergency frequency.

Word came Monday night that a crew from TAM, Brazil’s largest air carrier, saw orange spots on the ocean while flying over the same general area as the Air France Flight 447.

"If that was, in fact, debris burning from this aircraft, then that tells us that it broke up in flight," ABC News aviation consultant John Nance said Tuesday.

Air France said the captain of the flight had more than 11,000 hours of flight time, including 1,700 hours on the Airbus A330/A340.

There are 341 A330 planes of this type operating worldwide. Airbus released a statement saying it would be "inappropriate for Airbus to enter into any form of speculation into the causes of the accident.

"The concerns and sympathy of the Airbus employees go to the families, friends and loved ones affected by the accident," the statement read.

"The mid oceans are one of the remotest parts of the world," Hansman said. "It’s like going to the North Pole. It’s in an area where there is very limited ability to communicate."

ABC News’ Renata Araujo, Sonia Gallego, Joe Goldman, Christel Kucharz, Luis Martinez, Phoebe Natanson, Gabriel O’Rorke, Samira Parkinson-Smith, Kirit Radia and Christophe Schpoliansky, Reuters and The Associated Press contributed to this report.