Some Boeing 737s could have a rudder system malfunction, according to the National Transportation Safety Board. What the NTSB called “Urgent Safety Recommendations” apply to some of Boeing’s B-737NG and 737MAX planes, according to a statement on the NTSB website. The NTSB said the recommendation stemmed from its investigation of a Feb. 6 incident in which therudder of a United Airlines 737-8 MAX was stuck during landing. No one was hurt in the incident, and the captain used other features of the plane to control it. Investigators focused on a part called the rollout guidance actuator that was …