A passenger was killed and seven others needed medical treatment after an engine on a Southwest Airlines is believed to have exploded in mid air.
Witnesses say an engine on the left side blew, smashing a window and causing cabin depressurisation that nearly sucked a woman out of the aircraft.
She was pulled back in by other passengers.
The US internal flight made an emergency landing in Philadelphia after a window, wings and fuselage were damaged in the incident, according to local reports.
In an air traffic control recording, one of the pilots can be heard saying “there is a hole and someone went out”.
The Boeing 737-700 had been en route from New York’s La Guardia airport to Dallas, Texas, with 143 passengers and five crew when the incident occured on Tuesday morning.
The dead woman was named locally as Jennifer Riordan, a mother-of-two and bank vice-president at Wells Fargo in Albuquerque, New Mexico.
The US National Transportation Safety Board said a preliminary investigation had revealed that an engine fan blade was missing and there was evidence of metal fatigue at the point where it had apparently broken off.
NTSB chairman Robert Sumwalt said part of the cowling – the engine’s covering – was found in Bernville, Pennsylvania, about 70 miles from Philadelphia.
“It is very unusual so we are taking this event extremely seriously,” he said, adding that the investigation could take 12 to 15 months.
Sumwalt told reporters the type of engine, a CFM56, is “very widely used in commercial transport”.
Southwest Airlines said it was “devastated” and extended sympathy to all those affected by the “tragic event”.
The last passenger death on a US commercial flight was in 2009.