WASHINGTON (AP) — Safety investigators are making “urgent” recommendations to Boeing and the Federal Aviation Administration after determining pedals that pilots use to steer 737 Max jetliners on runways can become jammed because moisture can leak into a rudder assembly and freeze.

The National Transportation Safety Board issued the recommendations Thursday following its investigation of an incident earlier this year involving a United Airlines plane.

The FAA said United is the only U.S. airline affected by the recommendations, and it believes the parts susceptible to jamming are no longer in use.

Collins Aerospace, a Boeing supplier, determined that a sealed bearing was incorrectly assembled on actuators for rudders that pilots adjust to stay in the center of the runway after landing.

Collins told Boeing that the faulty work affected at least 353 actuators that were installed on some Max jets and older 737s, according to the NTSB.

The NTSB recommended that Boeing change flight manuals to remove advice that pilots use maximum pedal force to overpower a jammed rudder. The NTSB said that could create sudden rudder movement that might cause the plane to go off the runway.

The NTSB recommended that the FAA determine if actuators with incorrectly assembled bearings should be removed until replacements are available.

On Feb. 6, the rudder pedals on a United Airlines Boeing Max 8 became stuck as the plane rolled down the runway after landing at Newark Liberty International Airport in New Jersey.

The captain resorted to steering by using the tiller, a handle in the cockpit that turns the wheel under the plane’s nose. The plane veered on to a high-speed turnoff, but no injuries were reported among the 155 passengers and six crew members.