Dave Calhoun, president and CEO of aircraft manufacturing giant Boeing, admitted to employees in a meeting Tuesday that the company is "acknowledging our mistake" after the door plug of a 737 Max 9 blew out in midair during an Alaska Airlines flight last week, just minutes after the plane had taken off from Portland, Oregon.

"We're going to approach this number one acknowledging our mistake," Calhoun said in the meeting, a Boeing spokesperson confirmed to CBS News. "We're going to approach it with 100% and complete transparency every step of the way. We are going to work with the NTSB who is investigating the accident itself to find out what the cause is. We have a long experience with this group. They're as good as it gets."

No one was seriously hurt in the incident Friday night aboard Alaska Airlines Flight 1282. The plane, carrying 174 passengers and six crew members and bound for Ontario, California, was forced to make an emergency landing back in Portland.

In response Saturday, the Federal Aviation Administration temporarily grounded 171 Boeing 737 Max 9 aircraft worldwide for safety inspections. The FAA said Tuesday that "every Boeing 737-9 Max with a plug door will remain grounded until the FAA finds each can safely return to operation."

Calhoun said Tuesday that Alaska Airlines' ability to quickly ground its fleet of Max 9s with door plugs "prevented, potentially, another accident."

"When I got that picture, all I could think about – I didn't know what happened, so whoever was supposed to be in the seat next to that hole in the airplane," Calhoun reportedly told Boeing employees Tuesday. "I've got kids, I've got grandkids and so do you. This stuff matters. Every detail matters."

Calhoun expressed "huge thanks and compliments" to the pilots and flight attendants aboard the Alaska Airlines flight who "got that airplane back on the ground at a very tumultuous moment, under very scary circumstances."

"They train their lives to do that, but you don't know til you know," Calhoun said. "I hope most never know. But this crew, they stood the test and delivered the airplane back home to us."

National Transportation Safety Board chair Jennifer Homendy told reporters over the weekend that "we are very, very fortunate" no one was seated in the two adjoining seats closest to the detached door plug, whose purpose was to cover an unused exit door.

Alaska Airlines said the plane had just been delivered from Boeing on Oct. 31. Homendy also disclosed that pilots had reported that the same plane experienced three pressurization warnings, from cockpit dashboard lights, between Dec. 7 and Jan. 4. At least one occurred in-flight.

Both United Airlines and Alaska Airlines, which have canceled hundreds of flights due to the grounded planes, reported Monday that inspections of door plugs on grounded 737 Max 9s revealed "loose hardware" such as "bolts that needed additional tightening."

United said it believes the loose hardware on its grounded planes is the result of an installation issue, which would be the manufacturer's responsibility.

Investigators are increasingly looking at four unaccounted-for bolts that should have kept the door panel from flying off during the flight. NTSB officials have said they are not yet sure if the bolts on Alaska Airlines Max 9 "ever existed."

Furthermore, a class-action lawsuit was brought last month against Spirit AeroSystems, the manufacturer of the blown-out door plug, over allegations that its products had "sustained quality failures" and "frequently contained defects."

Investigators are trying to determine if Boeing has received damaged door plugs from Spirit Aerosystems in the past. 

Spirit AeroSystems had been a manufacturing unit of Boeing until it was spun off in 2005.

The lost door plug was discovered Sunday in the backyard of a teacher in the Portland metropolitan area. Two cell phones which were sucked out of the plane were also found on the ground in the Portland area, one of which was still working.

Homendy called Friday's event "an accident, not an incident," and Calhoun said he trusts the NTSB will determine the cause.

"I trust every step they take, and they will get to a conclusion," Calhoun said Tuesday. "…The FAA, who has to now deal with airline customers who want airplanes back in service safely and to ensure all the procedures are put into place, inspections, all the readiness actions that are required to ensure every next airplane that moves into the sky is in fact safe and that this event can never happen again."

— Aimee Picchi, Aliza Chasan, Kris Van Cleave and Brian Dakss contributed to this report. 

In:
• Boeing
• Alaska Airlines