Jason Redmond/AFP via Getty Images
The Boeing logo on the first Boeing 737 MAX 9 airplane is pictured during its rollout for media at the Boeing factory in Renton, Washington on March 7, 2017. / AFP PHOTO / Jason Redmond (Photo credit should read JASON REDMOND/AFP via Getty Images)
CNN  — 

The Federal Aviation Administration says it is opening an investigation into Boeing’s quality control after the violent in-flight failure of a door plug on a nearly new 737 Max 9.

In a new statement, the FAA says last Friday’s dramatic in-flight blowout on Alaska Airlines 1282 “should have never happened and it cannot happen again.”

The fuselage plug that blew off the aircraft Friday left a gaping hole in the side of the plane and ripped headrests off seats as the plane flew at 16,000 feet shortly after taking off from Portland, Oregon, carrying 177 people.

The FAA says the investigation will focus on whether Boeing “failed to ensure completed products conformed to its approved design and were in a condition for safe operation in compliance with FAA regulations.”

Boeing said it “will cooperate fully and transparently with the FAA and the NTSB on their investigations” in a statement Thursday.

The move comes after the two airlines that operate the Max 9 in the United States–Alaska Airlines and United Airlines—found either loose hardware or bolts in the assembly of door plugs on their aircraft. United Airlines says its discovery pointed to possible installation issues. The planes remain grounded pending details on FAA-mandated inspections. The FAA is still reviewing guidance on the inspections from Boeing.

On Wednesday, Boeing CEO Dave Calhoun admitted in an interview with CNBC that the door plug failure was a “horrible escape” of its manufacturing and quality control processes.

When asked what exactly happened, Calhoun told CNBC, “What happened is exactly what you saw, a fuselage plug blew out. That’s the mistake, it can never happen.”

In that interview, Calhoun emphasized that he is “confident” in the FAA’s ongoing work to “inspect each and every one of the airplanes” and make “certain that they’re in conformance with our design, which is a proven design.”

In a letter to Boeing, the FAA asked the plane maker to supply any information on the root cause and actions taken to prevent it from happening again. The FAA said Boeing now has 10 days to provide “any evidence or statements” to the agency.

The FAA’s investigation is separate from an investigation begun by the National Transportation Safety Board (NTSB), specifically into the incident itself.

NTSB spokesperson Eric Weiss said earlier this week that a preliminary report is expected in three to four weeks.

But in the meantime, the agency has recovered key items sucked out of the plane. On Sunday, a Portland schoolteacher found a piece of the aircraft’s fuselage that had landed in his backyard and reached out to the agency. Two cell phones that were likely flung from the hole in the plane were also found in a yard and on the side of the road and turned over to investigators.

NTSB Chair Jennifer Homendy told CNN’s “Anderson Cooper 360” Tuesday that the recovered fuselage plug has “quite a lot” it can tell investigators and “really was the missing piece in the investigation.”

The plane’s plug door will be sent to the NTSB’s lab for testing, Homendy said. Plugs are sometimes installed by manufacturer in place of an emergency exit door, depending on the configuration requested by an airline.

This is a developing story. It will be updated.