Delta Air Lines has approved a pilot's decision last month to cut short an Atlanta-to-Tokyo flight because crew members had trouble sleeping in their on-board bunks. Atlanta-based Delta also said that, after meetings with pilots, its engineers have proposed a bigger sleeping module that should enable crew members to rest more easily than the current one, called "the coffin" by pilots. Complaints about the module became public after Capt. Roscoe McMillan landed his MD-11 in Portland, Ore., on April 7 rather than continue on to Japan. The 110 passengers were transferred to another flight. Delta spokesman Bill Berry said the captain "said he took the action because he didn't think his relief pilots would be as sharp as they should be." The Air Line Pilots Assn., representing Delta's 9,000 pilots, said the snug bunk-bed units recently installed for long-haul flights had too little room and allowed too much outside noise to filter in.