There are major safety questions about airplane inspections after new findings from a federal investigation.

It comes after an explosion on an American Airlines plan at Chicago’s O’Hare Airport in 2016. NBC Charlotte learned a flaw inside the engine was to blame. However, the newly released report also questioned current inspection guidelines.

The Defenders investigative team looked into safety at Charlotte Douglas Airport, the second biggest hub for American Airlines.

NBC Charlotte obtained a copy of the NTSB report, which has pages and pages of photos, including images of the charred American Airlines plane after the fire. The Defenders asked experts if the same incident could happen again.

Peter Tkacik, a professor of mechanical engineer at UNC Charlotte, explained how blades spin inside a jet engine. NBC Charlotte learned a defect in what’s called the “turbine disk” was to blame, according to the NTSB’s new report. Microscopic cracks grew over the course of more than 5,000 flight cycles.

“At some point, two thirds of it bails in the last half second, and so it explodes and parts go everywhere,” said Tkacik.

The Defenders dug into another disturbing finding. The NTSB says current inspection guidelines would not find the problem. NBC Charlotte asked Tkacik if airlines needed to review the inspection process.

“Oh absolutely. I think they do a really good job of reviewing these things,” said Tkacik.

Tkacik said the turbine disk is especially under pressure during takeoff because of thermal stress, bending, and centrifugal force.

“So the question is how can you detect those little microbe cracks early on before you get to the rapid explosion point,” said Tkacik.

The NTSB report also found other issues during the Chicago incident, including the other engine wasn’t shut down. That’s because the pilot checklist didn’t differentiate between an engine fire in the air and on the ground. In addition, flight attendants were inadequately trained to communicate on intercoms through the evacuation, the report said.

“With time they go, ‘We never thought about if you have X, Y, Z, and L, and you might have a new problem,'” Tkacik told NBC Charlotte.

Passengers weren’t blameless either. The NTSB found many people refused to leave their belongings behind. Fortunately, the pilot was able to stop the plane before taking off. One passenger was seriously hurt during the evacuation.

“This could have been worse, if that rotor flung pieces half a mile away, if it flung them into the passenger compartment those people could have been in deep trouble,” said Tkacik.

In a video response to the NTSB report on this incident, American Airlines officials praised the pilots and flight attendants, saying their response resulted in a safe resolution.

Below is some of the written response American Airlines provided to the NTSB:

“American Airlines respectfully submits that the probable cause of this accident was a manufacturing defect in the HPT second stage disk that was introduced during the alloy forging process that was undetectable in service using the manufacturer-recommended and FAA- required inspection techniques. Contributing to the severity of the accident was the release of high-energy segments of the fractured disk which resulted in additional aircraft damage and rapid propagation of a fuel-fed fire.“

American Airlines has a robust safety culture, sound training programs for pilots and flight attendants, and well-proven operational and maintenance procedures. These aspects played a significant role in ensuring that the challenges faced by our passengers and crew aboard flight 383 were managed to a safe resolution. American Airlines is proud of the skill and professionalism demonstrated by our crewmembers and grateful for the trust our customers and employees place in us every day. We are committed to excellence in all aspects of our work.”