More than 2,600 Boeing Co. 737 jets registered in the US will need to have their oxygen generators inspected after multiple reports of some units shifting out of position, which could prevent them from providing oxygen in an emergency.

The Federal Aviation Administration ordered visual inspections of the generators on older 737 planes and the current Max models in a so-called airworthiness directive issued on Monday. Some of the planes will require additional work to make sure the generators are in the proper place.

Airworthiness directives are relatively common and used by regulators to address potentially unsafe conditions on aircraft. However, Boeing’s quality and safety record has been under close scrutiny following the midair blowout of a door plug on an Alaska Airlines flight in January.

Shares of Boeing slipped 0.9% at 1:07 p.m. in New York trading, erasing earlier gains. The stock has fallen almost 30% this year.