MISSING PLANE SHOCK REPORT: FLEW 4 HOURS AFTER VANISHING.....WSJ: Investigators Considering Whether Plane Was Diverted 'With Intention Of Using It Later For Another Purpose'... Satellite 'Debris' Spotting Comes Up Empty... LATEST UPDATES...

Malaysian Transport Minister
 Hishammuddin Hussein in
 Kuala Lumpur briefs media on
 the search mission on
Wednesday. Reuters

U.S. investigators suspect that Malaysia Airlines 3786.KU -2.04%Flight 370 stayed in the air for about four hours past the time it reached its last confirmed location, according to two people familiar with the details, raising the possibility that the plane could have flown on for hundreds of additional miles under conditions that remain murky.

Aviation investigators and national security officials believe the plane flew for a total of five hours based on data automatically downloaded and sent to the ground from the BoeingCo. BA -0.99% 777's engines as part of a routine maintenance and monitoring program.

WSJ has confirmed that the pilot had the ability to manually turn off the transponder on Flight MH370. A mid-air catastrophe could have destroyed it. Why is the transponder so significant? WSJ's Jason Bellini has #TheShortAnswer.

That raises a host of new questions and possibilities about what happened aboard the wide body jet carrying 239 people, which vanished from civilian air-traffic control radar over the weekend, about one hour into a flight to Beijing from Kuala Lumpur.

Six days after the mysterious disappearance prompted a massive international air and water search that so far hasn't produced any results, the investigation appears to be broadening in scope. more