The National Transportation Safety Board is urging "immediate action" to inspect the Pratt & Whitney jet engines in use in 725 Boeing 757 aircraft. In a letter to the FAA, the NTSB said damaged or missing lugs have been found in six PW2037 engines, raising concerns that broken pieces could puncture fuel tanks and cause a fire. "These discoveries raise serious concerns and warrant immediate action by the FAA," the letter said. An FAA spokeswoman said the agency was working with Pratt & Whitney to decide whether the problem was restricted to engines manufactured during a specific period. "We're looking for a little bit more of a surgical approach," she said. "This is not something where you just park the plane and look at the engine."