aviation Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot air ...

, uncontrolled airspace is

airspace Airspace is the portion of the atmosphere controlled by a country above its territory, including its territorial waters or, more generally, any specific three-dimensional portion of the atmosphere. It is not the same as aerospace, which is the ...

where an

Air Traffic Control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airs ...

(ATC) service is not deemed necessary or cannot be provided for practical reasons. It is the opposite of

controlled airspace Controlled airspace is airspace of defined dimensions within which air traffic control (ATC) services are provided. The level of control varies with different classes of airspace. Controlled airspace usually imposes higher weather minimums tha ...

. It is that portion of the airspace that has not been designated as Control Area, Control Zone, Terminal Control Area or Transition Area. According to the

airspace classes The world's navigable airspace is divided into three-dimensional segments, each of which is assigned to a specific class. Most nations adhere to the classification specified by the International Civil Aviation Organization (ICAO) and described be ...

set by the

International Civil Aviation Organization The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international sc ...

(ICAO), the uncontrolled classes of airspace are class F and G.

Class F

Class F (uncontrolled) is rarely encountered in ICAO member-states' airspace systems. In the UK, it was formerly a hybrid between class E (controlled) and G (uncontrolled) as Advisory Routes (ADRs). In the UK, all airspace previously designated as class F was re-assigned to either class E or G on 13 November 2014.

Class G

Individual countries designate different portions of airspace as class G, e.g. in the UK, airspace above FL660 (

Flight Level In aviation and aviation meteorology, a flight level (FL) is an aircraft's altitude at standard air pressure, expressed in hundreds of feet. The air pressure is computed assuming an International Standard Atmosphere pressure of 1013.25 hPa ...

660 or 66,000 feet) is uncontrolled and belonging to class G, while in the US, any airspace above FL600 (60,000 feet) is designated as class E and therefore controlled. Similarly, large parts of lower airspace in the UK are uncontrolled while in the US any airspace above 700-1200 feet up to FL145 (14,500 feet), not designated as any other class of airspace (A-D) belongs to class E and is controlled.

Air traffic control

ATC does not exercise any executive authority in uncontrolled airspace, but may provide basic information services to aircraft in radio contact. The aircraft commencing its flight in uncontrolled airspace, and subsequently proceeding into controlled airspace, should obtain clearance from the ATC unit in whose area the controlled part will begin. If a flight starts in controlled airspace but its subsequent portion will be uncontrolled, its clearance should be up to the point at which the controlled portion of the flight terminates. Flight in uncontrolled airspace will typically be under VFR. Aircraft operating under

IFR In aviation, instrument flight rules (IFR) is one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other is visual flight rules (VFR). The U.S. Federal Aviation Administration's (FAA) ''Instrument Fly ...

should not expect separation from other traffic: however, in certain uncontrolled airspace, this might be provided on an 'as far as is practical' advisory basis. Controlled flights should not be vectored (directed) by ATC into uncontrolled airspace except for weather avoidance or in an emergency.

References

Air traffic control {{Aviation-stub