Searchers have found the wreckage from a Pan Am flight that plunged into the ocean off Puerto Rico in 1952, an accident that killed 52 and led to requirements for the passenger safety briefings given on every commercial flight. The plane, the Clipper Endeavor, made a hard landing after losing engine power shortly after takeoff. The 17 passengers and crew who survived told investigators everyone lived through the landing, but panic set in as many passengers struggled to find life vests and the...