The U.S. National Transportation Safety Board (NTSB) on Monday said more than 40 foreign operators of Boeing 737 airplanes may be using planes with rudder components that may pose safety risks.

The NTSB last week 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 NTSB also disclosed Monday that 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," NTSB Chair Jennifer Homendy said Monday in a letter to FAA Administrator Mike Whitaker.

The NTSB 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.

The NTSB said 271 impact parts may be installed on aircraft in service operated by at least 40 foreign air carriers, while 16 may still be installed on U.S.-registered aircraft. It said up to 75 may have been used in aftermarket installation.

CBC News has reached out to Air Canada, WestJet, Flair Airlines and Sunwing Airlines to confirm whether or not they are among the 40 foreign air carriers referred to by the NTSB. 

CBC News has also contacted the Transportation Safety Board of Canada and is awaiting a response. 

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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 NTSB recommendations seriously and scheduled to do additional simulator testing in October.

An FAA corrective action review board met Friday and the agency said that it is "moving quickly to convene a call with the affected civil aviation authorities to ensure they have the information they need from the FAA including any recommended actions."

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 NTSB said Thursday are no 737s at U.S. 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 that it had informed "affected 737 operators of a potential condition with the rudder rollout guidance actuator." It did not immediately comment on Monday.

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