Uncontrolled airspace exists wherever a control service can't be provided for whatever reason, or is not deemed necessary, many of them are above mountains or oceans. According to the airspace classes set by ICAO both class F and class G airspaces are uncontrolled by definition. All airspace above a certain flight level is uncontrolled. This level varies from country to country, e.g.: flight level 660 in the United States and flight level 460 in Spain. Mount Cook, a mountain in New Zealand A mountain is a landform that extends above the surrounding terrain in a limited area. ... Ocean (Okeanos, a Greek god of sea and water; Greek ωκεανός) covers almost three quarters (71%) of the surface of the Earth. ... The world’s navigable airspace is divided into three-dimensional segments, each of which is assigned to a specific class. ... The International Civil Aviation Organization (ICAO), an agency of the United Nations, develops the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth. ... In aviation, a flight level is the nominal altitude of an aircraft referenced to a standard pressure datum, as opposed to the real altitude above mean sea level. ...

Air traffic control does not exercise any authority in uncontrolled airspace, but keeps radio contact with IFR traffic. Although IFR flight is possible in uncontrolled airspace, it is not recommended by the ICAO. This is because there might be unknown traffic flying VFR without radio contact. VFR is permitted even in extremely poor weather in Class G airspace. Daytime flight is permitted even if visibility is just one mile. Air Traffic Control Towers (ATCTs) at Schiphol Airport Air traffic control (ATC) is a service provided by ground based controllers who direct aircraft on the ground and in the air to ensure safe, orderly and efficient traffic flow. ... Wikipedia does not yet have an article with this exact name. ... An aircraft is any machine capable of atmospheric flight. ... The Verein für Raumschiffahrt (VfR - Spaceflight Society) was an association of amateur rocket enthusiasts active in Germany from 1927 to 1933. ...

A common misconception is that all aircraft in controlled airspace are under the direction of air traffic control. In fact, VFR aircraft are not even required to have a radio to fly in Class E airspace. The point is that, in Class E airspace, IFR traffic is controlled. Controlled airspace exists in areas where air traffic control is capable of providing traffic separation. ...

Importantly, uncontrolled airspace is not the same as an uncontrolled airport, which can exist in both class E and G airspaces. An uncontrolled airport uses a UNICOM or CTAF frequency to allow VFR and IFR pilots to coordinate and alert each other of their actions, while a towered, controlled airport relies on the work of an air traffic controller to maintain separation. CTAF, or Common Traffic Advisory Frequency, is the name given to a VHF radio frequency used at U.S. airports which do not have an active or on-site control tower, such as when some major airports close their tower overnight. ... The control tower at Schiphol airport. ... Air traffic controllers are persons who operate the air traffic control system to expedite and maintain a safe and orderly flow of air traffic and help prevent mid-air collisions. ...

See Airspace classes for a more formal description of the international classifications. The world’s navigable airspace is divided into three-dimensional segments, each of which is assigned to a specific class. ...