Over the centuries thousands of sailing ships have vanished into the vastness of the world's oceans. They sailed out of port and simply were never heard from again, but this is not something expected when a modern airliner lifts off from the end of the runway.

So far that is exactly what has happened to Malaysian Airlines Flight 370 and its 239 passengers. However, such a disaster is far from unheard of and there are many scenarios, both accidental and nefarious, that could explain the disappearance.

The flight left Kuala Lumpur on its way to Beijing four days ago, but an hour into the flight something went awry and it stopped communicating with ground control and disappeared over the South China Sea. So far a large and concerted effort by a dozen countries involving satellites, aircraft and ships has not turned up any evidence as to what took place.

Boeing has not commented on the disappearance, but airline pilot and blogger Patrick Smith has a few thoughts. His first is to only believe what we know for sure. That the plane suddenly lost contact with the outside world, next, there was no mayday call. Another possibly ominous sign is two of the passengers were traveling under fake passports, a possible sign of terrorism. A 777 crashed last year in San Francisco, indicating some type of issue with the aircraft and then there is the fact that sometimes planes just fall out of the air. That is what happened to Air France Flight 447 five years ago.

Possibly the most telling clue is known.

"Investigators also say the plane's transponder signal - a location and altitude signal that is tracked by air traffic controllers on the ground - disappeared suddenly. This would indicate a sudden loss of power, as would happen during an inflight explosion or breakup, for instance," he said.

However, this only deepens the mystery. If the flight simply crashed into the ocean it would have left a large debris field that probably should have been discovered.

A sailing vessel 150 years ago could at best be equipped with a compass and an accurate clock, that was it as far as technology was concerned. Arriving safely fell directly into the captain's hands. Whereas the Boeing 777 contained a galaxy of the most advanced communications and navigation equipment available. Quite simply, it could not get lost as long as its instruments and pilots were functioning.

On the search side of the equation is the amount of technology being used to find the plane or wreckage. The U.S. Navy has sent in a P-3 Orion surveillance plane. The Orion is equipped as a submarine hunter and has equipment that can locate metal objects on the ocean surface. Other naval and military aircraft are also invlolved.

Boeing's 777 website states the airplane is equipped with a state of the art navigation system including an enhanced ground proximity warning system. The plane also incorporated a new two-way digital data bus that was simpler, reduced weight and was more reliable than the old system and a better fly-by-wire flight control system. So, from a technical stand point the passengers were in good hands.