The US National Transportation Safety Board says more than 40 foreign operators of Boeing 737 aeroplanes may be using planes with rudder components that may pose safety risks. 

The board last week issued urgent safety recommendations about the potential for a jammed rudder control system on some Boeing 737 aeroplanes after a February incident involving a United Airlines flight. 

The board also disclosed it has learned two foreign operators suffered similar incidents in 2019 involving rollout guidance actuators. 

“We are concerned of the possibility that other airlines are unaware of the presence of these actuators on their 737 airplanes,” chair Jennifer Homendy said on Monday in a letter to Federal Aviation Administration (FAA) administrator Mike Whitaker. 

The transport safety board is investigating an incident in which the rudder pedals on a United Boeing 737 MAX 8 were “stuck” in the neutral position during a landing at Newark. There were no injuries to the 161 passengers and crew. 

Boeing shares fell 2.7% on Monday. 

The board said 271 impact parts may be installed on aircraft in service operated by at least 40 foreign air carriers and 16 may still be installed on US-registered aircraft and up to 75 may have been used in aftermarket installation. 

Homendy said she was concerned the FAA “did not take this issue more seriously until we issued our urgent safety recommendation report”. 

The FAA said it was taking the safety board’s recommendations seriously and scheduled to do additional simulator testing in October. 

United said last week the rudder control parts at issue were in use in only nine of its 737 aircraft originally built for other airlines; the components were all removed earlier this year. 

The board said on Thursday there are no 737s on US airlines operating with the affected actuators, which were installed in some 737 MAX and prior-generation 737 NG planes that included an optional landing system. 

Boeing said in August it informed “affected 737 operators of a potential condition with the rudder rollout guidance actuator”. 

- David Shepardson, Reuters