Phoenix–Mesa Gateway Airport, formerly Williams Gateway Airport and Williams Air Force Base, is an international airport in the southeastern area of Mesa, Arizona, 20 miles southeast of Phoenix, in Maricopa County. The airport, owned and operated by the Phoenix–Mesa Gateway Airport Authority, is a reliever airport for Phoenix Sky Harbor International Air…Phoenix–Mesa Gateway Airport, formerly Williams Gateway Airport and Williams Air Force Base, is an international airport in the southeastern area of Mesa, Arizona, 20 miles southeast of Phoenix, in Maricopa County. The airport, owned and operated by the Phoenix–Mesa Gateway Airport Authority, is a reliever airport for Phoenix Sky Harbor International Airport. It is a base for Allegiant Air.