Weeks after a door panel blew off of one of its Boeing 737 Max 9 jets mid-flight, Alaska Airlines has started to return some of the planes to service after each has been inspected. The airline recently gave "CBS Mornings" an exclusive up-close look at the effort to return the planes to service as mechanics evaluate the planes' door panels and the bolts holding them in place. Meanwhile, the National Transportation Safety Board is still investigating the incident on Alaska Airlines flight 1282, as the Federal Aviation Administration conducts its own investigation into Boeing.

Alaska Airlines grounded their 65 Max 9 planes preemptively before the FAA ordered a temporary grounding of Boeing's 737 Max 9 model after one of the planes, flying for Alaska Airlines, suffered a blowout in the middle of a trip from Oregon to California. One of the doors on the aircraft detached while the plane was in the air on Jan. 5, forcing an emergency landing in Portland and prompting "immediate inspections of certain Boeing 737 Max 9 planes," the FAA said at the time.

At a maintenance facility in Seattle, inspectors check the efficacy of door plugs on Alaska Airlines' Boeing 737 Max 9 planes. The process to inspect a single door panel takes around 12 hours, and first requires removing two rows of seats, plus all of the cabin interior, just to access it. Mechanics check that four key bolts lining the door panel are secure and functioning properly. 

But their initial check is followed by 20 pages of measurements that have to happen before that plug can be deemed safe and the airplane is put back into service.

"I would personally fly next to the door plug and put my kids there myself and fly with me, after they've gone through these inspections," said Jason Lai, the managing director of engineering at Alaska Airlines. Lai oversees the airline's engineering team as they work around the clock.

"You're checking for all the hardware, make sure they're in place, make sure all the hardware are tight," Lai explained of the inspection process. He added, "We have found some loose bolts and we need to document those."

Lai said the team has found more loose bolts "than we would like," noting that mechanics flagged quite a few aircrafts with that particular problem while examining door panels on the Boeing 737 Max 9. Inspectors have not identified any planes where bolts were missing from the panels, he told CBS News.

Investigators are still working to determine if those key bolts were in place when the door panel blew out of Alaska Airlines flight 1282, but that airline and United have both started to send Boeing 737 Max 9 jets back into the air as service resumes with the proper clearance. Alaska Airlines is bringing back up to 10 planes a day as inspections are completed. 

The inspection efforts are being tracked from the airline's network operations center, with the goal of completing the inspection work this week.

"We had to make sure that we had a safe and compliant path forward to operating these airplanes. So, we did take it very slow and steady," said Captain Brett Peyton, the managing director of network operations at Alaska Airlines. "But we have to make sure we have the safety element done first."

In:
• Federal Aviation Administration
• Boeing
• Alaska Airlines
• National Transportation Safety Board