(Reuters) -The Federal Aviation Administration (FAA) said it is adopting a new airworthiness directive for 13 Boeing 757-200 airplanes of U.S. registry over reports of cracking in the structure in and around the lavatory service panel.

Airworthiness directives are legally enforceable regulations issued by the FAA to correct an unsafe condition in a product.

The FAA said stress concentrations in the lavatory service panel access pan, the fuselage skin, and the stringer 22 attachment to the service panel are too high, causing fatigue cracking.

That, in turn, could result in an in-flight depressurization and reduced structural integrity of the aircraft if not addressed, the FAA said.

It said the directive impacts 757-200 planes modified by particular supplemental type certificates.