Brazilian search planes are recovering what officials say is the wreckage of Air France Flight 447 which disappeared Monday off Brazil's northern coast. The debris will be examined for serial numbers and other markings to confirm that it is the missing plane.  The Airbus A330 vanished about four hours after leaving Rio de Janeiro, bound for Paris.

Search planes found a 20-kilometer-long oil slick, apparently left by the Air France jet.

Flight 447 left Rio de Janeiro bound for Paris on Monday.  It carried 228 people.  Debris found in the ocean could offer clues on why the four-year-old airplane went down. 

"The nature of the debris, the density, the position, make no doubt that we have the first material evidence that are linked to Air France 447," said Commander Christophe Prazuck, a spokesman for France's military.

A meteorologist with AccuWeather tells VOA that Flight 447 may have encountered 160-kilometer-per-hour winds as it flew into strong storms along the equator.

The area is called the Inter-Tropical Convergence Zone. It's where the trade winds between the Northern and Southern hemisphere meet. 

U.S. pilots who fly this route say the zone's fierce thunderstorms carry moisture lower and therefore often do not appear on radar.

Paul Zurkowski, a commercial pilot who flies to South America, says darkened cockpits help. "We'll turn off the interior lights and turn on the exterior lights to see more of what's outside, more of the clouds," he said.

Some experts point to severe turbulence or lightning strikes as to the cause. But planes are built to withstand strikes, so pilots say it's doubtful that lightning would be catastrophic.

Zurkowski says a few years back his plane started shaking and he realized it had been struck, just below his seat.

"We didn't see any damage to the airplane airborne, it didn't affect our radios or navigation equipment," he said. "But it did put small holes in the airplane which were found by maintenance when we landed."

Shortly before it vanished, Flight 447 transmitted automatic messages reporting failures in its pressurization and electrical systems.

The Airbus is a "fly-by-wire" plane, meaning it relies totally on electricity to fly.  Ron Ball piloted the same type of plane - an A330 - before retiring. "It's just built like a truck," he said.

Ball says electrical failure on board flight 447 is unlikely.

"There's so many back-up redundant systems electrically that, even if you lost everything, there's a ram air turbine you can deploy underneath the airplane with a propeller of its own that spins up there, and you have a generator there that takes over everything," he said.

Ball thinks a structural problem brought down the plane.

Air traffic controllers heard no distress call or unusual messages from the pilots before the plane disappeared from radar.

"Whatever happened, in my opinion was so instantaneous and so overwhelming that they just didn't have time or the capability to do any of that," Ball adds.
The real answer may be at the bottom of this water.  The flight recorders will transmit a signal for 30 days.

"We are now in a race against time," said Jean-Louis Borloo, the French Transportation Minister.