An Air France flight carrying 228 passengers and crew crashed into the Atlantic Ocean on Monday en route from Rio de Janeiro to Paris.
Below are facts about the doomed flight and some of the speculation about what might have caused the disaster.
FLIGHT AF 447
2203 GMT - Air France says the plane, an Airbus A330-200, takes off from Rio airport with 216 passengers and 12 crew.
0148 GMT - The aircraft leaves Brazilian air force radar, flying normally at 35,000 feet at a speed of 453 knots.
0200 GMT - Air France says the plane crossed into a stormy zone with heavy turbulence.
0214 GMT - The plane sends automatic messages indicating an electrical fault, Air France says. Prime Minister Francois Fillon says messages were sent regularly over a three minute period showing all systems were out of order. Brazilian authorities are reported as saying messages also indicated a loss of pressure in the aircraft. No mayday or distress signal received.
0220 GMT - Air traffic controllers expect update from plane. Nothing happens. Soon after, it fails to enter Senegal airspace.
0910 GMT - Plane due to land in Paris, but never arrives. Half an hour later, Air France announces the plane is missing.
Whatever happened to the plane, it was brutal and catastrophic. Here are some of the possible issues.
STORM - Air France says a combination of circumstances could have led to the crash, notably citing lightning and turbulence. The plane flew into a notoriously stormy area that shifts around the Equator, known as the Intertropical Convergence Zone.
Weather experts contacted by Reuters and quoted on the Internet confirm there were storms in the area and that the plane flew through as many as three thunderstorm clusters.
Pilots fly around bad storms when possible, but although the conditions were rough, a source told Reuters two Lufthansa jets passed through the same area just before and after the Air France plane, suggesting that no one thought the weather to be exceptionally bad or dangerous.
Experts also say jets are designed to withstand lightning, but add that a direct hit might have disrupted the plane's radar and radio, which could explain the communications blackout.
LePoint.fr news website said on Tuesday that some external sensors on the plane appeared to have frozen, which might have compromised cockpit readings. There was no confirmation of this.
TURBULENCE - If the plane was brought down by natural causes, then turbulence is the most likely culprit. An article on www.weathergraphics.com explains how a sudden, isolated storm cell might have caused severe turbulence, adding that young updrafts caused by such a phenomenon are hard to detect and can be very powerful. Some aviation experts have drawn a parallel with a 2006 crash when a Russian aircraft plunged to earth near the Ukrainian border after hitting a storm and turbulence.
TECHNICAL FAILURE - Without the black box it is impossible to know what role, if any, technical problems played in the crash. While malfunctions were signaled by the plane, it is impossible to say if these were the cause of the crash or a side-effect of other problems.
TERRORISM - Both Air France and government ministers say they can rule nothing out, but have stressed that there is nothing to indicate terrorism was involved. An explosion would explain the sudden loss of the plane, but more than 24 hours after it vanished there have been no public statements claiming responsibility.