NEW YORK (REUTERS) - The wrecked engine of a Southwest Airlines jet was being examined on Wednesday (April 18) by US air safety officials investigating why it blew up in mid air, killing a passenger in the country's first deadly airline accident in nine years.

The engine exploded over Pennsylvania about 20 minutes after the Dallas-bound Southwest Flight 1380 left New York's LaGuardia Airport with 149 people on board, sending pieces of shrapnel into the plane.

Bank executive Jennifer Riordan, 43, was killed.

Southwest crews were inspecting similar engines the airline had in service, focusing on the 400 to 600 oldest of the CFM56 engines, made by a partnership of France's Safran and General Electric, according to a person with knowledge of the situation.

It was the second time that style of engine had failed on a Southwest jet in the past two years, prompting airlines around the world to step up inspections.

A National Transportation Safety Board (NTSB) inspection crew was also combing over the Boeing 737-700 for signs of what caused the engine to explode.

Passengers described scenes of panic as a piece of shrapnel from the engine shattered a window on the aircraft, almost sucking a female passenger out. Witnesses speaking with US media identified Riordan as the passenger nearly sucked out the window.

"The window had broken and the negative pressure had pulled her outside the plane partially," Peggy Phillips, a registered nurse who was on the plane, told WFAA-TV in Dallas.

"Two wonderful men... they managed to get her back inside the plane, and we laid her down and we started CPR."

'MY LAST FEW MOMENTS'

Videos posed on social media showed passengers grabbing for oxygen masks and screaming as the plane, piloted by 56-year-old Tammie Jo Shults, a former fighter pilot for the US Navy, prepared for its descent into Philadelphia.

"All I could think of in that moment was, I need to communicate with my loved ones," passenger Marty Martinez told ABC's Good Morning America on Wednesday. During the incident, he logged on to the plane's in-flight WiFi service to send messages to his family.

"I thought, these are my last few moments on Earth and I want people to know what happened," said Martinez, who live-streamed on Facebook images of passengers in oxygen masks as the plane made a bumpy descent into Philadelphia.

Southwest Airlines experienced an unrelated safety incident early on Wednesday when a Phoenix-bound flight was forced to land at Nashville airport shortly after takeoff because of bird strike.

The airline expected to wrap up its inspection of the engines it was targeting in about 30 days.

The GE-Safran partnership that built the engine said it was sending about 40 technicians to help with Southwest's inspections.

NTSB chairman Robert Sumwalt said on Tuesday 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 would normally be attached.

Pieces of the engine including its cowling - the smooth metal exterior that covers its inner workings - were found about 97km away from Philadelphia airport, Sumwalt said.

Sumwalt said the investigation could take 12 to 15 months to complete. NTSB officials said they would next update the public on their investigation at 4.30pm ET (4.30am on Thursday, Singapore time).

In August 2016, a Southwest flight made a safe emergency landing in Pensacola, Florida, after a fan blade separated from the same type of engine and debris ripped a hole above the left wing. That incident prompted the US Federal Aviation Administration to propose last year that similar fan blades undergo ultrasonic inspections and be replaced if they failed.

Riordan's death was the first in a US commercial aviation accident since 2009, according to NTSB statistics.

Riordan was a Wells Fargo banking executive and well-known community volunteer from Albuquerque, New Mexico, the company said.