In the United States, the Federal Aviation Administration (FAA) has the sole authority to regulate all "Navigable airspace", exclusively determining the rules and requirements for its use.[2] Specifically, the Federal Aviation Act provides that: "The United States Government has exclusive sovereignty of airspace of the United States" and "A citizen of the United States has a public right of transit through the navigable airspace."[3] The "navigable airspace" in which the public has a right of transit has been defined as "the airspace at or above the minimum altitudes of flight that includes the airspace needed to ensure safety in the takeoff and landing of aircraft."[4] However, this does not authorize the United States Government to operate aircraft with impunity in regards to "substantial impairment" of private property, which constitutes a governmental taking requiring just compensation.