New details emerge on piece of Alaska Airlines plane that blew off midflight as investigators probe ‘explosive decompression’

(CNN) — Federal officials examining the horrifying midflight blowout of part of an Alaska Airlines aircraft’s fuselage are testing the detached piece for clues on what led up to the plane’s “explosive decompression” after the missing piece was discovered in an Oregon backyard.

New details are emerging on the plane’s detached fuselage “plug door” and its components as both Alaska and United Airlines say they found loose hardware on a number of their Boeing 737 Max 9s, which for days have been grounded nationwide for inspections.

National Transportation Safety Board Chair Jennifer Homendy told CNN’s “Anderson Cooper 360” that the fuselage plug that blew out of the plane mid-flight Friday and was recovered from the yard Monday has “quite a lot” it can tell investigators and “really was the missing piece in the investigation.”

Investigators have so far determined the components that may have been involved in the refrigerator-sized door plug coming loose, but not yet determined why it blew out.

The door plug is typically held in place by a series of stop fittings and has a set of bolts that prevent the door from moving up and potentially flying off the plane mid-flight. Somehow, the plug on Alaska 1282 moved upward, NTSB’s Clint Crookshanks explained at a news conference Monday night.

“We have not yet recovered the four bolts that restrain it from his vertical movement and we have not yet determined if they existed there,” Crookshanks said. “That will be determined when we take the plug to our lab.”

“We don’t know if there were bolts there, or if they are just missing and departed when the door plug departed,” Homendy said at the news conference.

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.

“We’re able to look at all the components on this door plug, all the fittings, all – any sort of structures that may remain,” she said, adding metallurgists and materials engineers will be looking at bolts, washer, nuts and other components of the door.

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.

On Monday, a Portland schoolteacher found the door plug in his backyard and reached out to the NTSB, according to Homendy. Physics teacher Bob Sauer later told reporters he found the door plug intact in a tree’s lower branches, with one edge against the ground.

As investigators probe the plug door, unanswered questions remain over previous warnings about the plane’s pressurization and whether other Boeing aircraft are safe to fly.

Complicating the NTSB investigation is the loss of critical cockpit audio recordings because of a device setting, Homendy has said.

Homendy said the flight crew described the blowout as a “very violent, explosive event when it occurred” – something that’s apparent when looking inside the aircraft. There was damage to trim, insulation, windows and seats, she said.

Interviews with flight attendants have been very emotional, Homendy said Monday.

“There’s a lot of trauma that they are working through. It’s going to be a long process. It was terrifying.”

Airlines find loose hardware on Max 9s

On Monday, United confirmed it found the loose bolts on an undisclosed number of its 737 Max 9 aircraft as the company is performing FAA-mandated inspections following the Friday incident.

“Since we began preliminary inspections on Saturday, we have found instances that appear to relate to installation issues in the door plug –- for example, bolts that needed additional tightening,” United officials said in a statement. The United news was first reported by The Air Current, an aviation industry publication.

Alaska Airlines issued a statement later Monday saying technicians who were preparing to conduct their inspections had seen “some loose hardware was visible on some aircraft.”

The formal inspection process of Alaska Airlines’ fleet hasn’t started yet as they wait for final documentation from Boeing and the Federal Aviation Administration, the statement said.

For the NTSB, the focus is on the Alaska Airlines flight involved in Friday’s incident.

“Our focus right now is on this aircraft to determine what happened, how it happened and to prevent it from happening again,” Homendy said. “Once we determine that we can see if there’s a greater concern that we want to issue an urgent safety recommendation for.”

NTSB officials will continue the painstaking examination of the interior of the plane and the detached door plug, Homendy said.

171 planes grounded

Boeing said it agreed with the Federal Aviation Administration’s decision to ground the 737 Max 9 planes while they are inspected.

The order impacts about 171 aircraft “with a mid-cabin door plug installed.”

The FAA said the planes must be parked until emergency inspections are performed, which will “take around four to eight hours per aircraft.”

On Monday, Boeing said it sent airlines and maintenance companies instructions on how to inspect the planes. The FAA confirmed that it has signed off on those instructions.

The supplier that makes the fuselage of Boeing’s 737 Max jets, Spirit AeroSystems, said it is working with Boeing on the issue.

“We are grateful the Alaska Airlines crew performed the appropriate procedures to land the airplane with all passengers and crew safe,” the company said in a statement Monday. “At Spirit AeroSystems, our primary focus is the quality and product integrity of the aircraft structures we deliver.”

Alaska Airlines has also said it is working with Boeing to understand what happened on Flight 1282.

United, which has more Max 9s than any other US carrier, has canceled more than 470 flights since Saturday because of the Max 9 inspections. The inspection process requires removing two rows of seats and interior aircraft panels and requires five technicians, according to United.

Plane was restricted from flying over water amid auto pressurization fail lights

The airline had restricted the aircraft in Friday’s incident from flying over the ocean to Hawaii to ensure the plane could “return very quickly to an airport” in case any warning lights in the aircraft went off, according to Homendy.

That decision came after the plane’s auto pressurization fail light came on three times in the past month, Homendy said. It’s not clear whether there is a connection between the warning lights and Friday’s incident, she noted.

“At this time, we have no indications whatsoever that this correlated in any way to the expulsion of the door plug and the rapid decompression,” Homendy said of the pressurization fail lights in a Monday update.

While the repeated pressurization alert is “very disconcerting to investigators,” who are looking into the issue with Boeing and Alaska Airlines, Homendy said, “it may have absolutely nothing to do with what occurred in the cabin of the aircraft during that event.”

The fail light came on December 7 and on January 3 and 4 –- the days leading up to the blowout, she said. Each time, the flight crew flipped a switch to the system’s backup, Homendy said, describing the move as “very normal.”

“They flipped it, they reported it, it was tested by maintenance and then reset.”

“They did order additional maintenance to look at the light that was not complete before (the fuselage blowout). We plan to look at that more and we’ve requested documentation on all defects since delivery of the aircraft on October 31,” she said.

Homendy noted Monday that Alaska Airlines’ restriction on flying over water was not required by regulation. It was “put in place for Alaska as an extra step to ensure safety and to allow them to conduct maintenance.”

The plane involved in Friday’s incident had been in service for about three months and flown about 150 times since October 2023, according to FlightAware and FAA records.

Crew interviews, interior damage illustrate terrifying scene

Interviews with flight crew and the examinations of the damage left behind inside the cabin shed light on the loud, “violent” and chaotic scene inside the aircraft when the door plug tore off, causing an incredibly forceful depressurization and sending flight attendants rushing to the side of children on the flight, the NTSB chief said.

After the “explosive event,” flight attendants scrambled to ensure four unaccompanied minors onboard were wearing oxygen masks and lap belts, Homendy said, praising the attendants as “heroic.”

In the cockpit, the captain and the first officer heard a bang, then felt some air and some pressure changes in their ears and the cockpit door flew open. A flight attendant rushed to try and close it, Homendy said.

The captain and first officer described a very loud, chaotic environment, saying they had trouble hearing each other and air traffic control, according to Homendy.

The cockpit door was designed to open during rapid decompression – but flight attendants didn’t know that, Homendy said in a Monday night update.

“Boeing is going to make some changes to the manual, which then hopefully will translate into procedures and information for the flight attendants and for the crew in the cockpit,” Homendy added.

Several guests on the flight were injured and required medical attention but had all since been medically cleared, the airline said in a Saturday statement.

But “communication was a serious issue” between the pilots and flight attendants, who said they were having difficulty quickly sharing information, she added.

“I do want to emphasize that the actions of the flight crew were really incredible,” she said.

The impact of the event caused damage to the interior paneling, trim and plastic around the windows inside the plane, all of which are “not critical” to the aircraft’s structure, Homendy said.

The damage extended to several rows on the plane – not just the row next to the hole, according to Homendy. The two seats next to the door plug – 26A and 26B – were empty when the blowout happened, but had their headrests torn off, she said previously. The back of 26A is completely gone.

There was no structural damage to the aircraft and airframe, she noted.

Cockpit recorder setting wipes crucial evidence

The cockpit voice recorder, which captures sounds such as engine noises and pilots’ voices, was “completely overwritten,” since devices are currently only required to retain two hours of audio at a time, Homendy said.

“There is nothing on the cockpit voice recorder,” she said, noting the maintenance team went out to get the recorder around the two-hour mark when the devices begin a new recording cycle.

“We’re disappointed that the cockpit voice recorder was overwritten,” Homendy said Monday.

The audio captured by the recorders is “critical” to helping investigators understand what occurred during the incident, Homendy said. Without it, there is no record of communications between pilots and flight attendants as the crisis was unfolding.

“If that communication is not recorded, that is, unfortunately, a loss for (the NTSB), and a loss for the FAA and a loss for safety because that information is key not just for our investigation, but for improving aviation safety,” Homendy said.

Though the Federal Aviation Administration has proposed a new rule that would require new aircraft to extend their cockpit voice recordings to 25 hours, the rule would not require older aircraft to be retrofitted, Homendy noted. The NTSB chief called on the FAA and Congress to require 25-hour recordings in all aircraft.

“I cannot emphasize enough how important that is for safety,” she said.

CNN asked Alaska Airlines about about the wiped cockpit audio and the airline’s previous decision to restrict the plane from flying from over the ocean. The company replied in a statement Monday:

“Because this is an active investigation, we must receive permission from the NTSB to provide information about the aircraft and its prior maintenance,” Alaska Airlines said. “We have asked for permission from the NTSB to address these questions – they will not permit us to comment at this time. We will provide information as soon as the NTSB gives us permission to do so.”

Fallen cell phones may provide insight

Two cell phones that were likely flung from the plane were found in a yard and on the side of a road and turned in to investigators, who may be able to use them as evidence, Homendy said.

“Cell phones have actually helped us determine some things that occurred after tragedies … But it also helps in telling us, ‘Are we looking in the right area?,” the agency chief said just minutes before finding out the door plug had been discovered.

Sean Bates told CNN he spotted a phone on an Oregon roadside and turned it over to the NTSB, who were already in the area investigating the accident.

The phone didn’t have a security lock, and a photo of the phone shows an emailed Alaska Airlines baggage receipt for two bags, Bates said.

NTSB spokesman Jennifer Gabris told CNN that the agency took custody of the phone Sunday and has since turned the phone over to Alaska Airlines.

Community members also found a plastic window frame and a headrest and turned them into the NTSB, Homendy said Monday. The agency is still looking for a bottom hinge fitting and springs that were part of the door plug, she said, though noting those pieces aren’t critical to the investigation.

CNN’s Lauren Mascarenhas, Holly Yan, Joe Sutton, Mike Valerio, Anna-Maja Rappard and Chris Boyette contributed to this report.

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