Cris Tolomia
Quartz

The Federal Aviation Administration ordered inspections of 471 U.S.-registered Boeing 737 Max jets Thursday, saying that cracks in the fuselage, if left undetected, could jeopardize an aircraft's ability to withstand normal operating loads.

The directive covers Boeing 737-8, 737-9, and 737-8200 models. It applies to 1,429 planes worldwide and takes effect September 10, the FAA said. No cracks have been found in 737 Max jets specifically.

The cracks were found in older generation 737 planes in a structural component known as the bear strap, which reinforces the area around the forward service door on the right side of the aircraft near the front galley, the FAA said. Over time, the stress of takeoffs and landings can cause cracking near door corners.

Carriers are required to examine each aircraft according to a timetable tied to how much it has been flown and to fix any cracks discovered before the plane is cleared to resume operations. The FAA stopped short of grounding the fleet, explaining that the mandated inspection schedule gives operators several chances to catch any cracking well before it reaches a dangerous size.

Boeing said it alerted 737 Next Generation operators to the problem in 2019 and, five years later, broadened the inspection program to cover 737 Max jets on the grounds that the two families share comparable engineering and production methods. The company said it is conducting analysis to determine the root cause of the cracks and is working on manufacturing changes to prevent the issue in future aircraft.

Southwest Airlines told CBS News it was assessing the FAA's airworthiness directive and intended to carry out the required checks on the affected jets within the agency's prescribed timeframe. United Airlines said that it anticipates no disruption to its schedule in the coming months and plans to perform the checks as part of scheduled heavy maintenance, noting that its oldest Max jets have not yet accumulated enough flight cycles to trigger an immediate inspection.

The FAA estimates the inspections will cost U.S. operators $85 per airplane for an initial general visual inspection, with additional per-cycle costs of up to $340 for detailed and eddy current inspections.

The directive arrives less than a month after the FAA proposed a separate airworthiness directive requiring airlines to inspect seat installations on 453 Boeing 737 Max jets over concerns that improperly seated assemblies could disengage during turbulence or an emergency landing. That directive followed the FAA's decision to restore Boeing's authority to conduct final safety signoffs on newly produced 737s — a responsibility the agency had stripped from the manufacturer in 2019 following two fatal crashes involving the Max.

Boeing has faced a series of manufacturing quality issues in recent years. In January 2024, a door plug blew out of an Alaska Airlines 737 Max in flight. Investigators at the National Transportation Safety Board determined that the door plug had been delivered to the airline without four bolts that were required to secure it.

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This article was originally published in Quartz.

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