The pilot of the Air France flight that disappeared over the Atlantic Ocean sent a text message to the airline saying the plane had encountered bad weather, ABC News has learned.
As investigators examine communications sent from the plane before it vanished, searchers hunting for clues on the Atlantic today found a 23-foot piece of airplane at sea, Brazilian air force spokesman Col. Jorge Amaral said.
Watch "World News with Charles Gibson" Tonight at 6:30 p.m. ET for the full report.
Several other teams of people on planes and ships are still making their way to the remote crash site with equipment to recover debris -- including a French search and exploration ship, due to arrive at the crash site Friday, equipped with robots that can plunge about 20,000 feet underwater to help recover wreckage.
That's the same team that worked with Dr. Robert Ballard to find the Titanic in the 1980s.
Ballard has a unique perspective on what lies ahead in the underwater search for missing Air France flight 447.
"Heavy objects will go to the bottom very, very rapidly," said Ballard, director of the Center for Ocean Exploration and Archeological Oceanography at the University of Rhode Island. "Lighter objects are carried for great distances, much like the lifeboats of the Titanic were miles and miles away from where we actually found the Titanic. And in many ways, the debris they're finding are like the lifeboats of the Titanic, floating on the surface, being carried further and further."
A forensic scientist is also believed to be onboard one of the planes on its way to help with the recovery operation. The U.S. Coast Guard is assisting in the effort to provide a "reverse drift" simulation, working backwards to help determine where the plane's fuselage might be based on where wreckage is floating.
Bad weather is meantime 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.
"The terrain here is worse than the terrain where we lost the Titanic," Ballard added. "The Titanic is sort of like in the Badlands of the Dakotas compared to the Rocky Mountains."
The flight from Rio de Janeiro to Paris vanished with 228 people onboard Sunday night. On Tuesday searchers found an oil slick and debris from the plane floating in the Atlantic 700 miles off the coast of Brazil.
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.
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.