May 4 (UPI) -- Federal investigators say broken fragments of an engine cowling, not a fan blade, broke a window on a deadly Southwest Airlines flight last month.
The National Transportation Safety Board said Thursday the cowling -- the protective cover that shields the engine compartment -- forced Southwest Airlines flight 1380 to make an emergency landing in Philadelphia April 17.
"The engine experienced a failure of a fan blade, which resulted in the loss of the engine inlet and cowling," the NTSB said. "Fragments from the cowling and engine inlet struck the fuselage, causing a rapid depressurization."
Officials said the fan blades on the aircraft's engine were last overhauled in November 2012 -- 10,712 engine cycles before the accident.
The NTSB initially thought a blade, which showed cracks consistent with metal fatigue, broke off and damaged the cowling, left wing, left horizontal stabilizer and fuselage.
The flight, from New York City to Dallas, carried 144 passengers and five crew.
Passenger Jennifer Riordan was partially expelled from the broken window, and later died at a Philadelphia hospital. Medical examiners said she died from blunt force impact trauma to the head, neck and torso. Eight other passengers received minor injuries.
According to the NTSB, passengers experienced vibrations and heard a loud sound during the flight. Oxygen masks were automatically deployed.
Passengers and flight crew members reported experiencing a sudden change in cabin pressure, aircraft yaw, cockpit alarms and a "gray puff of smoke."
The plane rolled left to about 40 degrees before the flight crew was able to counter the roll with control inputs, NTSB said.
The pilot of the aircraft, Tammie Jo Shults, was praised for "nerves of steel" and keeping calm as she planned the emergency descent. Shults, members of the crew and passengers of the ill-fated flight met with President Donald Trump at the White House earlier this week.