The China Eastern Airlines Corp. jet was flying a normal route to Guangzhou when it suddenly nosed over, at cruise altitude, and dove.

That¡¯s about all that is known for certain about the unusual crash that killed all 132 people aboard the aircraft Monday in China¡¯s worst aviation accident in more than a decade.

While there have been a handful of crashes in which an airliner plunged from cruising altitude, few, if any, fit the extreme profile of the Boeing Co. 737-800 as it pointed steeply toward the ground, according to veteran crash investigators and previous accident reports.