Philadelphia: An engine on a Southwest Airlines flight with 149 people aboard exploded and broke apart in mid-air on Tuesday, killing one passenger and nearly sucking another out of a shattered window, according to airline and federal authorities and witness and media accounts.

The plane, a Boeing 737-700 which was bound to Dallas from New York, made an emergency landing in Philadelphia.

The death of 43-year-old Jennifer Riordan on Flight 1380 was the first in a US commercial aviation accident since 2009, according to National Transportation Safety Board (NTSB) statistics.

NTSB Chairman Robert Sumwalt told an evening news conference at the Philadelphia airport that a preliminary investigation found an engine fan blade missing, having apparently broken off, and that there was metal fatigue at the point where it normally attached.

Sumwalt said part of the engine's covering, called a cowling, was found in Bernville, Pennsylvania, about 70 miles from the Philadelphia airport. "It is very unusual so we are taking this event extremely seriously," Sumwalt said." This should not happen and we want to find out why." Reuters