CFM is a joint venture of General Electric and France's Safran.
John Goglia, a former NTSB member, said investigators will take the Southwest engine apart to understand what happened and will look at maintenance records for the engine. A disk within the GE CF6-80 engine was later found to have a manufacturing defect, the NTSB said.
"One passenger, a woman, was partially...was drawn out towards the outside of the plane...was pulled back in by other passengers", he said.
One passenger broadcast the terrifying descent on Facebook Live. He added that there was a fuel leak and a small fire when firefighters arrived.
He didn't release any additional details on the landing.
Amanda Bourman, of NY, said that the woman was taken off the plane by emergency medical workers Tuesday after the emergency landing around 11:20 a.m.
One passenger says the plane was fairly quiet because everyone was wearing an oxygen mask, while some passengers were in tears and others shouted words of encouragement. The NTSB investigates the most serious engine failures and conducted a probe of a similar Southwest incident in 2016 involving the same type of engine.
"There are various iterations of that [engine] and so I can't say exactly what that air worthiness directive might have applied to at this point, but that will be part of our investigation", he said.
The plane, bound for Dallas from New York's LaGuardia airport, landed shortly after 11am on Tuesday (April 17) at Philadelphia International Airport.
Passengers were seen walking off the plane on the tarmac at the airport and the left engine of the plane is damaged. It wasn't immediately known if anyone aboard the plane was hurt.
Last year, the engine maker and the Federal Aviation Administration instructed airlines to make ultrasonic inspections of the fan blades of engines like those on the Southwest jet.
According to 6ABC.com, Southwest Airlines Flight 1380 was traveling from New York City's LaGuardia Airport to Love Field in Dallas, Texas, when the left engine of the aircraft suffered a mid-flight failure.
Tracking data from FlightAware.com showed Flight 1380 was heading west over Pennsylvania about 32,200 feet (10 kilometres) and traveling 500 miles per hour (800 km/h) when it abruptly turned towards Philadelphia. "Emergency landing! Southwest flight from NYC to Dallas!" he wrote. "Something is wrong with our plane!"