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”.