The US Federal Aviation Administration warned operators of certain Boeing Co. 737 aircraft that the rudder system could possibly jam due to a faulty part, a week after a safety official rebuked the agency for not acting sooner to address the issue.

The NTSB criticized the FAA for a desultory response to the risk from faulty 737 rudders and Boeing for not fully informing airlines in advance about them.

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 regulator said operators of the Boeing 737 NG and 737 MAX airplanes with SVO-730 rudder rollout guidance actuators should give specific instructions to flight crews.

The U.S. Federal Aviation Administration (FAA) on Tuesday issued a safety alert informing operators of the potential for limited or jammed rudder movement on certain Boeing (NYSE:BA) 737 airplanes. The FAA issued a so-called Safety Alert for Operators (SAFO).