Miles City Airport or Frank Wiley Field is a city-owned airport two miles northwest of Miles City, in Custer County, Montana, United States. The airport was served by one airline, subsidized by the Essential Air Service program. EAS subsidies ended on July 15, 2013, due to subsidy per passenger exceeding $1000, leaving Miles City without scheduled air …Miles City Airport or Frank Wiley Field is a city-owned airport two miles northwest of Miles City, in Custer County, Montana, United States. The airport was served by one airline, subsidized by the Essential Air Service program. EAS subsidies ended on July 15, 2013, due to subsidy per passenger exceeding $1000, leaving Miles City without scheduled air service.