The National Transportation Safety Board issued urgent safety recommendations to Boeing over a steering defect related to its 737 planes, adding its growing list of woes.

The National Transportation Safety Board on Thursday issued urgent safety recommendations about the potential for a jammed rudder control system on some Boeing 737 airplanes after a February incident involving a United Airlines flight.

The National Transportation Safety Board is issuing “urgent safety recommendations” for some Boeing 737s—including the embattled 737 MAX line— warning that critical flight controls could jam.