The Federal Aviation Administration has ordered inspections of hundreds of Boeing 737 Max jets after cracks were found in parts of some older model Boeing planes.

The FAA Thursday issued fuselage inspections for certain 737 Max 8, 737 Max 9 and 737-200 models after reports of cracks were discovered in the structural reinforcement around the forward service door near the galley on the right side of some older generation 737 planes. 

The directive applies to 471 planes in the U.S. and 1,429 planes worldwide, according to the FAA. So far, no cracks have been found in Boeing Max jets specifically. The order, though, sets a timeline for mandatory inspections to catch cracks and make any needed repairs before they become a safety issue.

The FAA said the cracks that were found in the older planes had developed in what is known as the bear strap, which reinforces areas around doorways and emergency exits. Over time, the stress of takeoffs and landings can lead to cracking near door corners.

In a statement provided to CBS News, Boeing said it first notified operators of its 737 Next Generation planes of the issue in 2019, when it provided them with “detailed instructions for conducting the recommended inspections.”

Boeing said that although the issue has not so far been observed in its 737 Max fleet, in 2024, it “extended the inspections to 737 MAX airplanes as the model shares a similar design and build process” to its Next Generation model.

Boeing said it is also conducting analysis to determine the root cause of the cracks and prevent them in future aircraft.

Southwest Airlines, which is one of the primary operators of 737 jets in the U.S., told CBS News in a statement that it was “reviewing” the FAA’s airworthiness directive and “will accomplish the inspections on the affected airplanes according to the schedule specified by the FAA.”