The Federal Aviation Administration (FAA) has notified operators of the Boeing 737 Next Generation and Max series about a possible problem with the rudder control system.

The National Transportation Safety Board (NTSB) had previously made an urgent safety recommendation after a United Airlines flight encountered a failure involving a Collins Aerospace component known as the rudder rollout guidance actuator in February.

Following this incident, the NTSB expressed concern in a letter between its officials and the FAA, indicating that the FAA was not adequately addressing the potential dangers associated with this component.

In the notice, the FAA advises airlines to inform their crews about the potential issue.

The bulletin specifies: “Operators of Boeing 737NG and 737MAX aircraft equipped with Collins Aerospace SVO730 RRGA should inform pilots that the rudder control system may become jammed or restricted during flight or landing due to moisture that could freeze within the RRGA actuator.” The document then provides a series of recommended actions for pilots to follow in case of component failure, depending on the flight phase.

The NTSB notes that there are hundreds of the affected parts currently in operation with airlines worldwide, although it is not clear how many are installed on aircraft registered in the U.S.