Last Friday, an Alaska Airlines flight from Portland, Ore., to Ontario, Calif., experienced a harrowing failure when a body panel called a “door plug,” attached in place of an unneeded exit door, blew out and off the plane.

The Boeing 737 Max 9 was only about six minutes into its flight when the door flew off, leaving a gaping hole in the fuselage. Air roared out of the plane with great force, ripping the shirt off a youth strapped into a seat nearby, pulling open the cockpit door so that it slammed into the cabin wall and knocking off a co-pilot’s headphones. Fortunately, despite the depressurization, the heroic pilots were able to stabilize and land the damaged plane.

But make no mistake: the incident was life-threatening. Passengers or a flight attendant near the blown-out plug could have been sucked out of the plane if not belted into their seats. The cabin was depressurized, forcing passengers to don those taken-for-granted oxygen masks that automatically drop from the ceiling.

The incident, along with flaws quickly discovered after follow-up inspections of Max 9s used by both Alaska and United airlines, led the Federal Aviation Administration (FAA) to order all Max 9s grounded, calling on manufacturer Boeing to revise safety protocols to guarantee detection and repair of any other potential flaws. This pulled 110 to 150 flights daily off Alaska Air’s schedule at least through this Saturday, including Hawaii flights, and spotlights the vulnerability of an island state to all aspects of airline operations.

As a matter of law, and because passengers’ lives literally depend on a plane’s readiness to fly, it’s mandatory that at each step of design, manufacture, inspection and operation, stringent safety protocols are imposed to prevent tragic flight failures before they can occur. There must be zero tolerance for laxity — and yet, indications are that oversight flagged at crucial points in preparing this Max 9 for flight.

The door plug that few off was recovered, but examiners have been unable to locate four bolts that were supposed to secure the panel to the plane body, and can’t yet confirm that the door was properly bolted down. That such a serious flaw wasn’t detected via existing safety protocols is frightening to consider, and indicates that safety checks must be examined and improved to eliminate this or any other potential flaw.

On Thursday, the FAA announced that its investigation would focus on the door plugs, and a full review must be conducted to pinpoint the junctures where safety may have been subpar. If the door plug design is faulty, that would be traced to Boeing. The plugs were installed by Boeing subcontractor Spirit AeroSystems, so if faulty installation is revealed, it could be held responsible. If the blowout happened because inspections and maintenance standards were too lax, Boeing could still be responsible because it issues inspection parameters, or alternatively, some division of responsibility with the airline might be found.

Alaska’s handling of the plane that lost its door plug also deserves scrutiny. Three low-pressure warnings — two the day before this incident — had triggered additional scrutiny of the plane, but when crews couldn’t pinpoint the source of the problem, the decision was made to prevent flying the plane over open ocean, as with flights to Hawaii. It must be asked: If there’s concern that a trans-ocean flight could be unsafe, shouldn’t there be concern that any flight could be unsafe?

The FAA has not concluded that Alaska should have grounded the plane, or even that the warning lights and panel blowout were related, but that’s being investigated. These findings will be vital to assessing both the decision to fly this plane as well as the airline’s safety protocols.

All of this is of vital concern to Hawaii, with Alaska poised to take over Hawaiian Air, and may equally concern regulators. Manufacturers, airlines and regulators must apply the highest standards to earn passengers’ trust and ensure confidence in flying.