The federal government has jurisdiction over United States airspace. No individual may claim ownership of airspace over his or her property. Airspace is considered to be public domain and may be used by anyone as long as they do not interfere or endanger the people and property on the ground below. Once an aircraft pushes back from the gate, the airport no longer controls the movements or actions of the aircraft. The responsibility is shifted to the pilots and Air Traffic Control (ATC). The FAA determines which runways are in use for arrivals and departures or the pilot at an uncontrolled airport. Air Traffic Controllers are employed by the U.S. government or by private companies who are contracted by the U.S. government.