The US Federal Aviation Administration has ordered inspections of hundreds of Boeing 737 Max aircraft after cracks were reported in a structural component on older 737 models. The measure is intended to identify any similar weakness before it can affect the aircraft’s structural integrity, adding to scrutiny of Boeing’s safety and production practices.

The directive applies to an estimated 471 US-registered 737 Max 8, Max 9 and 737-8200 aircraft, and takes effect on 10 September. No cracks have been found on the affected Max models so far; the concern arose because their design and manufacturing process are similar to those of older 737 Next Generation aircraft where cracking was reported.