PORTLAND, ORE. -- The emergency began with a bang three miles above Oregon.

The first six minutes of Friday's Alaska Airlines flight 1282 from Portland to Southern California's Ontario International Airport had been routine, the Boeing 737 Max 9 about halfway to its cruising altitude and travelling at more than 400 mph.

As the plane climbed, the cabin's air pressure steadily increased, a normal occurrence in comparison to the rapidly thinning air outside. The plane's four flight attendants and 171 passengers sat strapped in their seats, nearly filling its 178-passenger capacity.

Then boom.

A 2-foot-by-4-foot piece of fuselage covering an unoperational emergency exit behind the left wing blew out. The force of the cabin air being sucked outside in a deafening rush twisted the metal bracing holding the seats next to the hole and ripped off their headrests -- which by fate, were two of the few unoccupied seats.

The near-vacuum also ripped open the locked cockpit door, sucked away the pilots' one-page emergency checklist and pulled off the co-pilot's headset. More than a dozen other seats, some far from the hole, were damaged by the force. Some passengers had their cellphones ripped from their hands and sucked out. Passengers said one teenager had his shirt ripped off. Dust filled the cabin.

"All the oxygen masks deployed instantly and everyone got those on," Evan Smith, an attorney travelling on the plane, told KATU-TV.

The pilots and flight attendants have not made public statements and their names have not been released, but in interviews with National Transportation Safety Board investigators they described how their training kicked in. The pilots focused on getting the plane quickly back to Portland and the flight attendants on keeping the passengers' safe, and as calm as possible.

"The actions of the flight crew were really incredible," NTSB Chair Jennifer Homendy said at a Sunday night news conference. She described the scene inside the cabin during those first seconds as "chaos, very loud between the air and everything going on around them and it was very violent."

Inside the cockpit, the pilot and co-pilot donned their oxygen masks and opened their microphone, but "communication was a serious issue" between them and the flight attendants because of the noise, Homendy said. The pilots retrieved an emergency handbook kept secure next to the captain's seat.

The co-pilot contacted air traffic controllers, declaring an emergency and saying the plane needed to immediately descend to 10,000 feet, the altitude where there is enough oxygen for everyone onboard to breathe.

'We need to turn back to Portland," she said in a calm voice that she maintained throughout the landing process.

In the cabin, the flight attendants' immediate focus was on the five unaccompanied minors in their care and the three infants being carried on their parents' laps.

"Were they safe? Were they secure? Did they have their seat belts on or their lap belts on? And did they have their masks on? And they did," Homendy said.

Some passengers began sending messages on social media to loved ones. One young woman said on TikTok that she was certain the plane would nosedive at any second and she wondered how her death would affect her mother, worrying that she would never recover from the sorrow.

But she and others said the cabin remained surprisingly calm. One passenger, Evan Granger, who was sitting in front of the blowout, told NBC News that his "focus in that moment was just breathe into the oxygen mask and trust that the flight crew will do everything they can to keep us safe."

"I didn't want to look back and see what was happening," he said.

The pilots circled the plane back to Portland. Video taken by passengers showed flight attendants moving down the aisle checking on passengers. City lights could be be seen through the hole flickering past.

Smith told reporters the descent and landing were loud but smooth. When the plane touched down at Portland International about 20 minutes after it departed, the passengers broke into applause. Firefighters came down the aisle to check for injuries, but no one was seriously hurt.

"There were so many things that had to go right in order for all of us to survive," Granger told NBC.

Homendy said that if the blowout had happened a few minutes later, after the plane reached cruising altitude, the accident might have become a tragedy.

On Sunday, a passenger's cellphone that had been sucked out of the plane was found. It was still operational, having survived its three-mile plunge.

It was open to the owner's baggage claim receipt.

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Spencer reported from Fort Lauderdale, Florida.