1. Lightning Strike
Lightning appears to be the most plausible cause for the disappearance of Flight 447. But it’s still unlikely that lightning alone could bring down such a big jet like an Airbus 330. After all, jets are engineered to weather lightning strikes without severe damage. When lightning hits, it usually does so on the aluminum body of the plane at the wings—far from the engine and the insulated plastic cabin where the passengers sit. Only 50 minutes after making contact via radar, Flight 447 reported via an automatic transponder that it had an “electrical circuit malfunction,” which means it could have fallen victim to an electrical storm. If a lightning strike did indeed damage the fuselage, aviation expert Clive Irving writes, it should be regarded as a serious warning for engineers of new planes like the carbon-fiber Boeing 787 Dreamliner, which is being designed without metal. "Because no airliner has ever been built this way before," he writes, "the 787’s ability to demonstrate a level of lightning protection at least equal to a conventional all-metal airplane is crucial."
“A completely unexpected situation occurred on board the aircraft," said Air France’s CEO.
2. Violent Turbulence
We know that Flight 447 encountered heavy turbulence associated with a thunderstorm before losing signal. At 4:14 a.m. Paris time, the plane released an automatic message that it had suffered an electrical problem and lost cabin pressure. But what caused that? It's possible that the plane flew into a fierce tropical storm over the Atlantic Ocean, The Washington Post reports, but pilots are trained to go around tropical storms—never through them. And the pilot of Flight 447 must have known that: He had clocked more than 11,000 hours in the air—including 1,100 hours on the Airbus jets. According to a senior meteorologist for AccuWeather, the thunderstorms in that part of the Atlantic Ocean towered up to the 50,000 feet that night—which could mean that the plane flew into the most treacherous part of the storm. Thunderstorms at that altitude, the Times of London reports, can have the “energy of nuclear explosions.” According to Pierre Henri Gourgeon, chief executive of Air France-KLM: “Lightning alone is not enough to explain the loss of this plane, and turbulence alone is not enough. It is always a combination of factors… A completely unexpected situation occurred on board the aircraft.”
3. Hail Storm
Just before the plane fell off the map, it reported a loss in cabin pressure—which could mean a break in the body of the aircraft. If Flight 447 flew into a particularly violent storm, The New York Times reports, it’s possible that hail could have broken the windshield. But pilots would have immediately reported distress had that happened—not just drop off the radar altogether.
4. Electrical Failure
We know that Flight 447 experienced an electrical failure before losing contact. But experts say a simple electrical fault doesn’t bring down an Airbus—so if the electrical outage is responsible, it must have developed into something greater. The Airbus was as “fly-by-wire” plane, which means that the flaps on the wings are commanded by wires rather than manual tubes. This allows planes, in many circumstances, to automatically correct if something goes wrong. But this electronic control can also backfire, as it did with an Australian Qantas A330 last year: When something goes wrong on some fly-by-wire planes, the pilot is blocked from overriding commands. On the Qantas jet, inertia sensors overrode manual commands, causing the plane to correct something that wasn’t wrong—and a nosedive resulted.
5. Fire on Board
The electrical fault may have also caused a short circuit, which, according to David Learmount, operations/safety editor of FlightGlobal, can create an intense heat or sparking on the plane. That could have resulted in a fire, which brought down a Swiss Air Boeing jet in 1998. There’s been a call for smoke detectors to be placed throughout aircrafts—not just in the bathrooms, cargo area, and engines—so that crew members can be informed of fire on board, but it's so far been largely ignored by airlines.
6. Hijacking or Sabotage
Theories of sabotage or hijacking circulated following news of the disappearance, but have been all but dismissed as aviation experts weigh the facts. There were no suspicious people on board, the Times of London reports, and had a hijacking occurred, the crew would surely have time to radio to the base.
7. Missile or Bomb
The Times of London also speculates that a missile could have caused the disappearance, but that it’s “highly unlikely given the altitude.” It’s also conceivable that a bomb may have exploded on board—explaining its immediate disappearance from radar—as the Times reports that security at the Rio airport is widely thought to be lax.
Isabel Wilkinson is a Daily Beast intern who attends Columbia Journalism School. She has written for New York magazine and Women’s Wear Daily.