Alaska Airlines cancels all 737 Max 9 flights through Jan. 13. Here's what we know about the door plug investigation.

Alaska Airlines announced Wednesday it has decided to cancel all flights on 737 Max 9 airplanes through Saturday, Jan. 13, as it waits for Boeing and the Federal Aviation Administration to provide instructions on inspections of the specific aircraft.

“We hope this action provides guests with a little more certainty, and we are working around the clock to reaccommodate impacted guests on other flights,” the airline said in a statement posted to its website. The decision will affect 110 to 150 flights per day, the airline said.

On Saturday, the FAA ordered grounding of all Boeing 737 Max 9 airplanes that have a midcabin door plug installed until they pass inspection. Alaska and United are the only two U.S. airlines that utilize Max 9 models.

United said Wednesday it was also waiting for final instructions on the inspection process, and it canceled 167 flights. The airline canceled 150 more flights Thursday and said it expected additional “significant cancellations” to come, the Washington Post reported.

United and Alaska also said they discovered loose parts on multiple Max 9 planes during initial checks of the aircraft.

Last Friday, Alaska Airlines Flight 1282 was forced to make an emergency landing shortly after takeoff in Portland, Ore., after a door plug failed in midair, leaving a large hole in the side of the plane. The plug has since been recovered and the National Transportation Safety Board is investigating the cause of the incident.

Incredibly, none of the 171 passengers and six crew members on board Flight 1282 were seriously injured.

Here’s what else we know about the investigation:

The door plug

The recovered door plug from Alaska Airlines Flight 1282 is being taken to a lab in Washington, D.C., to be examined as part of the NTSB’s investigation. The agency said Monday evening that it has yet to recover four bolts that kept the door plug in place. It is unclear whether the bolts were fractured, loose or weren’t ever installed in the first place, the NTSB said.

NTSB Chair Jennifer Homendy told reporters Monday that the door plug on the right side of the fuselage, opposite of the one that blew off, was examined Monday and there were “no discrepancies,” but that further inspections would be conducted.

The dislodged door plug was found Sunday in the backyard of the home of Portland resident Bob Sauer, a high school physics teacher.

“It was unbelievable that that thing that people had been looking for all weekend happened to be in my yard,” Sauer told NBC News.

The NTSB visited Sauer and his students in his classroom on Tuesday.

The warning light

The plane used on Flight 1282 had other issues as well. After a warning light signaling a pressurization issue went off during three previous flights, the plane had been restricted from longer routes to Hawaii that travel over open water. That restriction was put in place in the event the warning light reappeared so as to enable the plane to quickly return to an airport. The warning light had previously gone off on Dec. 7, Jan. 3 and Jan. 4, just one day before the door plug flew off.

“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 told reporters on Monday evening. “We will go back and look at the flight data recorder and we will get data on cabin pressure and we’re also going to download the memory on the cabin pressure controllers.”

More experiences surface from the flight

A teenage boy on the Alaska Airlines flight had his shirt “sucked off” when the door plug blew off, USA Today reported.

Kelly Bartlett, a fellow passenger on the flight, wrote on Instagram that she heard a loud boom as the plane filled with wind and noise as the oxygen masks dropped. She noticed there was a hole in the side of the plane three rows behind her. “There was one open seat next to me, and a 15-year-old kid jumped over me, sat down, and grabbed the mask," Bartlett wrote. “He had no shirt on because it had been sucked off when the panel blew.”

Because of the noise and oxygen masks, she couldn’t talk with the 15-year-old, who said his name was Jack. Instead, she opened her notes app on her phone to communicate with him to see if he was OK. Jack said he was fine, Bartlett wrote, but she could see redness and scratches on his back that could have been caused by windburn.

Boeing’s ‘mistake’

Spirit AeroSystems, the Boeing contractor that builds the 737 Max 9 fuselages, said in a statement Wednesday that the company is cooperating with the NTSB investigation.

Boeing CEO Dave Calhoun spoke out about the midair door plug blowout, calling it a “mistake.”

“We’re going to approach this, number one, acknowledging our mistake. We are going to approach it with 100% in complete transparency every step of the way,” Calhoun said Tuesday during a meeting with employees.