An American Airlines Group Inc. unit that operates regional flights has grounded most of its fleet to conduct inspections on aircraft doors.

The checks involve bolts on the nose-gear doors of most or all of PSA Airlines Inc.’s fleet of 130 Bombardier Inc. CRJ700 and CRJ900 regional jets, said Sarah Jantz, a spokeswoman for American. The company is booking affected passengers on other flights while working with the U.S. Federal Aviation Administration to return the planes to service.

“Out of an abundance of caution, PSA Airlines has temporarily removed most of its aircraft from service in order to complete a necessary, standard inspection on the nose-gear door,” American said in an email. “We are working with PSA and the FAA to immediately address the issue.”

PSA had canceled 110 flights, or 23% of its schedule, as of 12:30 p.m. Eastern time, according to tracking service FlightAware.com. It had also delayed 94 flights, FlightAware data showed.

The regional carrier, which is wholly owned by American, is headquartered in Dayton, Ohio.