The attempt by an off-duty pilot to shut down the engines of a U.S. airliner in midflight highlights the threat that insiders pose to aviation safety with their ability to go where passengers are prohibited. The captain and co-pilot prevented disaster by subduing the off-duty Alaska Airlines pilot who — from his perfect vantage point in the cockpit jump seat — tried to cut fuel to the engines. The pilot who was arrested after Sunday's flight didn't appear to raise alarms.