Phoenix Sky Harbor International Airport is a civil-military public airport 3 miles east of downtown Phoenix, in Maricopa County, Arizona, United States. It is Arizona's largest and busiest airport, and among the largest commercial airports in the United States; in 2021, PHX was the 8th-busiest airport in the United States and 11th-busiest in the world. The airport serves as a hub for American Airlines and a base for Southwest Airlines. In 2021, Southwest carried nearly 35% of all PHX passengers, making it the airport's largest carrier and surpassing American for the first time in years. The airport is also home to the 161st Air Refueling Wing, an Air Mobility Command-gained unit of the Arizona Air National Guard. The military enclave is known as the Goldwater Air National Guard Base. One of two flying units in the Arizona ANG, the 161 ARW currently flies the KC-135R Stratotanker aircraft. In addition to its domestic role as a National Guard unit, answering to the Governor of Arizona, the 161 ARW also performs both a stateside and overseas role as a USAF organization, supporting air refueling and air mobility missions worldwide.