The Federal Aviation Administration directed airlines to inspect 453 Boeing 737 MAX jets registered in the United States after finding some passenger seats were installed incorrectly.

The directive was prompted by a report that an undetermined number of track-mounted passenger seat assemblies were not correctly installed in the seat tracks, the FAA said in a proposed airworthiness directive published July 27.

"The unsafe condition, if not addressed, could result in injury to passengers and crew during an emergency landing or could block the aisle, which could slow evacuation," the FAA said. "A track-mounted passenger seat assembly that is installed incorrectly can disengage from the seat tracks if there is an increased load, turbulence, or emergency landing."

The FAA said the issue traces to seat locking pins that were not correctly lowered and engaged in the seat tracks. The directive covers Boeing 737-8, 737-9 and 737-8200 models.

The FAA estimates the inspections will cost operators up to $2.6 million to review. The FAA is accepting public comments on the proposed directive through September 10.

Boeing said it welcomed the FAA making the inspection guidance mandatory for operators, according to the Wall Street Journal.

The directive affects about a fifth of the more than 2,300 MAX jets in service, the Journal reported.

The finding came less than two weeks after the FAA restored Boeing's authority to issue final safety signoffs on newly produced 737 jets, a privilege the agency revoked in 2019 following two fatal MAX crashes.

Boeing is also awaiting final FAA certification of the smaller 737 MAX 7 and the larger MAX 10, a process delayed by manufacturing problems including a January 2024 incident in which a door plug detached from an Alaska Airlines jet.

That incident led to the temporary grounding of dozens of 737 jets and a proposed FAA fine of more than $3 million for what the agency called safety violations.

Boeing has faced additional safety scrutiny this month after a window came loose on an older 737 variant operated by Ryanair, partially pulling a passenger toward the opening before the plane diverted safely.