737 Max 9 grounding extended as aviation bosses say they'll prioritize safety, not speed over the Alaska Airlines blowout

• The FAA temporarily grounded Boeing 737 Max 9 jets with a plug door due to the Alaska Airlines incident.
• United Airlines and Alaska Airlines found loose bolts during inspections.
• The jets won't fly again until each has been inspected with revised instructions from Boeing.

All Boeing 737 Max 9 aircraft with a plug door will remain grounded until the Federal Aviation Administration finds each jet "can safely return to operation," the FAA announced Tuesday.

"The safety of the flying public, not speed, will determine the timeline for returning the Boeing 737-9 Max to service," it added.

There are 171 such planes around the world, mostly in the US. With 79 in service, United Airlines is the largest operator of the 737 Max 9, followed by Alaska Airlines, which has 65.

It means disruption to travelers will go on longer than initially expected following last Friday's Alaska Airlines incident.

Flight 1282's plug door, which covers a deactivated emergency exit, was blown off in midair, causing a rapid depressurization with oxygen masks deployed. The plane returned to Portland International Airport 20 minutes after taking off with no serious injuries to passengers.

As a result, Alaska Airlines voluntarily grounded its fleet for inspection, and 18 returned to service before the FAA issued an Emergency Airworthiness Directive on Saturday.

Boeing then gave operators of the 737 Max 9 instructions for the inspections.

But both United and Alaska found problems during these inspections. United found loose bolts on the plug doors of several aircraft, while Alaska said "some loose hardware was visible on some aircraft."

Now, Boeing is revising its initial version of instructions in response to feedback, the FAA said.

The agency said it will "conduct a thorough review" of Boeing's instructions.

In a statement, Boeing said, "We continue to be in close contact with our customers and the FAA on the required inspections. As part of the process, we are making updates based on their feedback and requirements."

Alaska Airlines said it had canceled 109 flights on Tuesday due to the grounding.

"The safety of these aircraft is our priority and we will take the time and steps necessary to ensure their airworthiness, in close partnership with the FAA," it added.