The U.S. National Transportation Safety Board on Tuesday called on Boeing Co to redesign the fan cowl structure on 737 NG planes after a passenger was killed on a Southwest Airlines plane in April 2018 after an engine failure. The NTSB said the engine failure was caused by a broken fan blade, and the board said the U.S. Federal Aviation Administration should require Boeing to determine the fan blade impact location or locations on the engine fan case and redesign the structure to minimize the potential of a catastrophic failure.