(CNN) -- A Boeing 777, one of the world's most reliable types of airliners, is missing, and no one knows why. Was it a bomb? Mechanical failure? A hijacking gone awry? Pilots and others in the aviation community are deeply disturbed by the mystery surrounding Malaysia Airlines Flight 370.
It disappeared Saturday en route from Kuala Lumpur to Beijing over the Gulf of Thailand, somewhere between Malaysia and Vietnam. It's hard to believe that such huge questions remain three days after the Boeing 777-200ER went missing, carrying 227 passengers and 12 crew members. These questions are so unprecedented that experts have been carefully speculating about possible explanations.
Here are three scenarios they're talking about, and the related facts:
1. Scenario: Bomb? Or 'dry run'?
Fact: Two stolen passports have been linked to people who bought tickets for the flight.
Analysis: This points to the possibility that someone on a terrorism watch list may have boarded the plane and blown it up. However, the stolen passports don't necessarily mean the plane was an actual target. It's possible, says former U.S. Department of Transportation Inspector General Mary Schiavo, that terrorists may have been performing a "dry run" for a future attack. Or, Schiavo said, "it could be just criminal business as usual," because "there are lots of stolen passports" used by travelers around the world.
Fact: So far, no debris field of plane wreckage has been linked to the 777, which would indicate a bomb blast.
Analysis: When Robert Francis, former vice chairman of the U.S. National Transportation Safety Board, heard about the missing plane, his immediate thought was: "For some reason the aircraft blew up and there was no signal, there was nothing." The fact that the plane disappeared from radar without warning indicated to Francis "there was something unprecedented that hasn't happened before."
What about satellite technology? Is it possible that data from orbiting satellites might show a flash or infrared heat signature from an explosion? Very unlikely, says satellite expert Brian Weeden, who spent years tracking space junk in orbit for the U.S. Air Force. Dozens of government and private satellites orbit the earth, looking down from distances from 300 kilometers to 1500 kilometers (185 to 930 miles). It's a long shot that one of them coincidentally floated over at the exact right time and location to capture a flash from an explosion.
However, there's an "off chance," Weeden says, that a super secret U.S. government satellite orbiting 22,000 miles in space might have grabbed evidence. These satelllites are in geosychronous orbit. As a group, they can observe virtually the entire globe. "We know that their mission is to detect ballistic missile launches via heat," says Weeden, now a technical adviser for Secure World Foundation. "We don't know if they're sensitive enough to track something like a bomb blast, even if that's what happened."
Then there's another unanswerable question: Would the government hesitate to release such an image for fear of revealing the satellite system's ultraclassified capability?
2. Scenario: Hijacking?
Fact: Before it disappeared, radar data indicated the plane may have turned around to head back to Kuala Lumpur. Is that a clue that a hijacker had ordered the plane to change course?
Analysis: So far, there have been no reports that the flight crew sent any signals that a hijacking had occurred.
3. Scenario: Mechanical failure?
Fact: The absence of a debris field suggests the possibility that pilots were forced to ditch the plane and it landed on water without breaking up, finally sinking to the ocean floor.
Analysis: But if that were the case, then why no emergency signal? These planes are able to perform a "miracle on the Hudson" maneuver. They have the ability to glide more than 100 miles and belly land on the water with both engines out, says former 777 pilot Keith Wolzinger, now a civil aviation consultant with The Spectrum Group. During the time it would take for a plane to glide 100 miles, it seems likely that pilots would be able able to send an SOS.
Fact: The missing plane had suffered a clipped wing tip in the past, but Boeing repaired it, and the jet was safe to fly, said Malaysia Airlines CEO Ahmad Jauhari Yahya on Sunday.
Analysis: "Anytime there's been previous damage to an airplane, even though it's been repaired, and repaired within standards ... it kind of sends a warning flag," says Wolzinger. Experts agree the Boeing 777 is one of the world's most reliable aircraft. During its development it was subject to some of the most rigorous testing in commercial aviation history. "I've been talking with colleagues," Wolzinger says. "We're all baffled by this." The 777 boasts some of the most powerful and well-tested engines in the world, he says. "The reliability of airliner engines in general is impeccable these days," he says. "This is a safe plane."