In the wake of a near-catastrophe in the air, officials in the U.S. were searching on Sunday for a door that blew off an Alaskan Airlines plane loaded with passengers.

Canadian airlines are reassuring air travellers that they don’t fly the kind of plane involved in this incident, but the close call in mid-air has raised several safety questions.

With images of this terrifying incident in the air going viral, a former Canadian air crash investigator says the key now is getting a look at the door that was there.

“Critical to the investigation and determining cause of failure, will be finding that door, that plug. When you have all the pieces, you have the airplane frame, and if you have the door you can look now what was the mode of failure and what was the cause of failure,”
Dave Rohrer of the Warplane Heritage Museum said.

The plane had just taken off from Portland, Oregon on Friday and was still climbing when the door fell off.

The wind pulled one boy’s shirt off, but nobody on the plane was seriously injured, a total of 177 passengers and crew.

“We are very very fortunate here in that this didn’t end up in something more tragic,” Jennifer Homendy from the U.S. Transportation Safety Board said.

READ MORE: No Canadian airline fleets operate the Boeing 737-9 Max

The U.S. Federal Aviation Administration grounded 171 of the planes this weekend, the Boeing 737 Max 9.

The part of the plane that fell off was a so-called “door plug” that fills in an area where an emergency door can go in some models.

But the plane design itself is decades old, and experts question Boeing’s decision to load it up with modern technology instead of spending the money to re-design a new plane.

“They’ve taken an airplane that was designed in the 60s built in the 60s and 70s and put a lot of technology and a lot of stuff into that airplane that it was never designed to handle,” John Gradek of McGill University Aviation Management said.

The Max 9 is a longer version of the 737 Max 8, the kind of plane involved in a crash in Africa in 2019 that killed 157 people including 18 Canadians, with an automated flight control system implicated.

Boeing is still being sued over that crash and the lawyer says this latest incident is challenging confidence in the industry.

“The fact remains that people are afraid to fly when they think that safety is being compromised and some operator is trying to juice up their revenue or some manufacturer is trying to lower the cost of production that erodes the confidence of the public and their sense of safety,” Lawyer Robert Cooper said.

U.S. aviation officials say American planes with the same kind of door plug will stay grounded until officials are convinced they’re safe.