There's always a risk in flying, but the phase in which a plane is cruising at high altitude is widely considered to be safe. And that's what makes the mystery of what happened to Malaysian Airlines Flight MH370 so confounding.
"Whatever happened happened quickly and resulted in a catastrophic departure from the air," Mark Rosenker, former chairman of the National Transportation Safety Board who is now a consultant with CBS news, told NPR's Melissa Block.
There have been a number of cases in which planes have fallen from the sky — from factors that include catastrophic failure and sabotage. As Patrick Smith, a commercial pilot who runs the popular Ask The Pilot website, writes:
"All we know for sure is that a plane went down with no warning or communication from the crew. That the crash did not happen during takeoff or landing — the phases of flight when most accident occur — somewhat limits the possibilities, but numerous possibilities remain. The culprit could be anything from sabotage to an inflight fire to a catastrophic structural failure of some kind — or, as is so common in airline catastrophes, some combination or compounding of human error and/or mechanical malfunction."