The new Airworthiness Directive (AD), issued on Thursday, applies to an estimated 471 U.S.-registered Boeing 737 MAX 8, MAX 9 and MAX 8-200 aircraft. The directive takes effect on September 10.

According to the FAA, the inspections were prompted by reports of cracks in the bear strap and fuselage skin around the forward upper corner of the forward galley door cutout, located near the forward service door on the right side of the aircraft.

"The FAA is issuing this AD to address cracks in the fuselage skin and bear strap, which may lead to the inability of the principal structural element to sustain limit loads and adversely affect the structural integrity of the airplane," the agency said.

Airlines have been instructed to inspect the affected area based on each aircraft's usage and repair any cracks before returning the airplane to service. However, the FAA did not ground the affected aircraft, saying the inspection intervals provide multiple opportunities to detect damage before it poses a safety risk.

Boeing said it has completed an engineering analysis to determine the cause of the cracking and is developing design changes to prevent similar issues in the future.

"This issue has not been observed on the 737 MAX fleet, but Boeing extended the inspections to 737 MAX airplanes as the model shares a similar design and build process," the company said. "We support both directives and continue to support our airline customers."

The latest directive adds to Boeing's ongoing safety challenges. In 2019, the FAA ordered inspections of certain Boeing 737-700, 737-800 and 737-900 aircraft after structural cracks were found in a component linking the fuselage to the wings.

Last month, the FAA also proposed another airworthiness directive requiring inspections of seat assemblies on 453 Boeing 737 MAX aircraft over concerns they may have been installed incorrectly.

Boeing has remained under heightened regulatory scrutiny since a door plug detached from an Alaska Airlines 737 MAX 9 shortly after takeoff in January 2024. Investigators later found that four bolts intended to secure the door plug were missing when the aircraft was delivered to the airline in October 2023.