Federal safety watchdogs on Friday called on U.S. aviation regulators to mandate stringent repetitive inspections of all General Electric Co. engines used on Boeing Co.'s 787 and newest 747 models, citing a "threat of multiple engine failures on a single aircraft."

The National Transportation Safety Board's urgent recommendation follows two previously reported safety incidents on the ground with GE's newest engine type, plus a third instance of a problem the board disclosed in its letter to the Federal Aviation Administration....