TOKYO — An unexploded U.S. bomb from World War II that had been buried at a Japanese airport exploded Wednesday, causing a large crater in a taxiway and the cancellation of more than 80 flights but no injuries, Japanese officials said. [time-brightcove not-tgx=”true”] Land and Transport Ministry officials said there were no aircraft nearby when the bomb exploded at Miyazaki Airport in southwestern Japan. Officials said an investigation by the Self-Defense Forces and police confirmed that the explosion was caused by a 500-pound U.S.