The National Transportation Safety Board (NTSB) has flagged fresh concerns with Boeing's 737 planes, saying that at least 40 airlines outside the US may be operating aircraft with faulty components.

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

The U.S. National Transportation Safety Board on Monday said more than 40 foreign operators of Boeing (NYSE:BA) 737 planes may have rudder components that could be a safety risk. The warning came after the NTSB last week issued urgent safety recommendations about the possibility of jammed rudder control systems on some 737 airplanes.