A missing door plug that could be key to the investigation into what caused it to detach from a plane midflight Friday has been found in the backyard of a Portland, Oregon-area resident, officials said Sunday.

After the end of a news conference in which National Transportation Safety Board Chair Jennifer Homendy laid out the probe’s status, she returned to give a piece of positive news: “I’m excited to announce that we found the door plug,” she said.

Identifying the resident who sent two photos of the item to the NTSB only as Bob, a schoolteacher, she said, “Thank you, Bob.”

“We’re going to go pick that up and make sure that we begin analyzing it,” Homendy said.

Two cell phones have also been found — one in a yard and another on the side of the road, she said.

At the end of the first full day of the NTSB investigation into the accident on board Alaska Airlines Flight 1282, the agency’s chair indicated that some factors were complicating the probe: The plane’s cockpit voice recorder’s record of the event was inadvertently taped over, and, at the time, the door plug had not been found.

“That is unfortunately a loss for us,” Homendy said, lamenting the loss of voice data and sounding frustrated during a news conference Sunday night, “Because that information is key, not just for our investigation, but for improving aviation safety.”

Homendy said the NTSB is calling for expanding the minimum time recorded on the devices from two hours to 25 hours. Such a time span would have saved the cockpit voice data from Friday’s accident.

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

The device from Friday’s flight automatically recorded over the pertinent voice data because someone failed to power it down, she said. It starts a fresh recording, wiping out the last one, every two hours.

“The circuit breaker was not pulled,” Homendy said.

‘They heard a bang’

She described chaos and communication issues on board the Boeing 737 Max 9 as flight crew reported hearing a loud noise and the cabin rapidly depressurized Friday evening over the Portland area.

“They heard a bang,” she said.

The plane’s first officer lost her headset in the depressurization, and the captain had headset problems, as well, Homendy said. So they turned on a speaker for communication, she said.

“Communication was a serious issue,” Homendy said.

At the same time, the cockpit door opened violently, and a laminated checklist pilots use in an emergency situation flew out, the chair said.

“It did blew open during the explosive decompression,” Homendy said of the cockpit door.

The pilots turned to another quick reference guide, a handbook, she said, as a flight attendant took three tries to shut the cockpit door.

“The actions of the flight crew were really incredible,” Homendy said. “It was very violent when the door was expelled out of the plane. There was a lot going on.”

Homendy described some of the damage inside the plane. It included two seats, unoccupied by chance, that sustained such violent force that their frames had “torqued.”

Both seats in row 26 were missing their headrests, and one was missing a seat back. In all, damage was found along 12 of the plane’s seat rows, she said.

She expressed concern over three babies who were held in the laps of their caregivers. The NTSB, the Federal Aviation Administration and Alaska Airlines all recommend, but don’t require, that young children travel in car seats secured in separate, ticketed seats.

The FAA has ordered some Boeing 737 Max 9 airplanes, the model flown in the Alaska Airlines incident, to be grounded and issued a directive requiring inspections before certain aircraft can fly again. The new directive affects 171 planes worldwide.

When the FAA sent out its airworthiness directive, it is followed by a multi-operator message (MOM) from the manufacturer, in this case Boeing. The document is very specific on what the airline must do to accomplish the process for inspection.

Boeing typically works with the airlines and the FAA to finalize its inspection process, which ultimately must satisfy the FAA.  Boeing shares their progress with the FAA as the instructions are drafted and when it’s final, it’s submitted for final approval. Once approved, the airlines will follow the memo to inspect the grounded 737-9 aircraft, a process that the FAA said could take between four and eight hours.

A source familiar with the process said the MOM has been sent to United and Alaska airlines and inspections can start as soon as Monday.

Analyzing the door plug

Investigators are looking at how the door plug — a panel where an optional emergency exit can be placed depending on passenger capacity — was fastened before it blew out of the plane, Homendy said during Sunday night’s news conference.

They also want to know more about air pressurization alerts that went off on the plane during flights on Dec. 7 and on Wednesday and Thursday, the latter being the days before the accident.

She said the airline prohibited the aircraft from embarking on long flights over water — specifically from traveling to Hawaii — until the issue could be checked out more thoroughly. By Friday night’s flight from Portland to Ontario, California, that inspection hadn’t been completed, Homendy said.

She said the issue had been described to the NTSB has “benign” and that it was unclear whether there was any correlation between those alerts and Friday’s accident.

Homendy said investigators were focused in part on how the door plug was fastened and whether there were failures related to it, although she said the structural integrity of the aircraft was intact following the accident.

She described two hinges at the bottom of the plug that allow a small degree of opening for routine inspections as well as four “stop fittings” in the shape of circles.

“The purpose is to prevent that door plug from being pushed out of the air frame,” she said.

All those elements will get a close look, Homendy said.

This article was originally published on NBCNews.com