CHART: Plane Accidents Are Remarkably Rare At Cruising Altitude

A Malaysia Airlines 777 jet with more than 200 people on board has been missing for four days, and now military officials say the plane turned off course, then flew at least 350 miles with its tracking systems turned off.

Part of the mystery is that air accidents are most common when the plane is taking off or landing - not steadily flying at 35,000 feet. But that's where Malaysia flight MH370 seems to have encountered trouble.

This chart, from a Boeing report on worldwide commercial jet accidents between 1959 and 2012, shows how rare it is for a plane to suffer an accident while at cruising altitude. The report does not include accidents caused by natural causes, sabotage, military action, hijacking, or terrorism.

Even though planes spend about 57% of their time cruising, only 9% of fatal accidents happen during that phase of flight. Those accidents account for 18% of onboard fatalities, however - the seven accidents at cruise altitude included here led to 774 deaths.

For the report, Boeing used the International Civil Aviation Organization (ICAO) definition of an accident, an occurrence in which someone is fatally or seriously injured, the aircraft sustains damage, or the aircraft is missing or completely inaccessible.

Here's the chart, which shows that final approach and landing are the most dangerous parts of flight. Click to enlarge: