Japanese. Don't know when such signage was added. As to why: 1. Wikipedia (http://en.wikipedia.org/wiki/Detroit_Metropolitan_Wayne_County_Airport) says ... read more
Detroit Metropolitan Airport has maintenance facilities capable of servicing and repairing aircraft as large as the Boeing 747-400. In 2016, Detroit Metropolitan Wayne County Airport was the 18th-busiest airport in the United States. In terms of aircraft operations (takeoffs and landings), the airport was 18th-busiest in 2013. read more