Federal regulators say Boeing's grounded 737 Max 9 aircraft will stay grounded until they're shown to be safe for travelers.
The Federal Aviation Administration ordered a temporary grounding of certain active 737 Max 9 planes on Saturday, Jan. 6, after an incident in which a door blew out of an airborne plane operated by Alaska Airlines.
In a statement Tuesday, the FAA said the planes would return to flight only after they were shown to be safe.
"Boeing must provide instructions to operators for inspection and maintenance. Boeing offered an initial version of instructions [Monday] which they are now revising because of feedback received in response."
The FAA says it will make a thorough review of the updated instructions once they're available.
The grounding affects an estimated 171 planes that operate in U.S. territory or under U.S. carriers.
Regulators on Monday told reporters they were trying to determine if four bolts meant to hold the door in place had ever been installed in the affected plane. While the National Transportation Safety Board has recovered the door itself, the bolts have still not been located.
Alaska Airlines had already grounded its fleet of 737 Max 9 planes following the incident. The loss of the plug door required the crew and passengers to don oxygen masks and forced an emergency landing at Portland International Airport.
There were no serious injuries from the depressurization.
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