Air or Airspace
(1) (a) “Air” or “airspace” means the air up to the highest altitude at which an aircraft can fly and below the lowest possible perigee of an earth satellite in orbit. Under international law, airspace is classified as either national airspace (that over the land, internal waters, archipelagic waters, and territorial seas of any State) or international airspace (that over contiguous zones, exclusive economic zones, the high seas, and territory not subject to the sovereignty of any State).
[Commentary]
- Every State has sovereignty over the airspace above its land and water territory.[31]
- Until the advent of the first artificial satellites in 1957, it was widely assumed that national airspace had no upper limit. However, once artificial satellites were launched into orbit around Earth, it soon became obvious that the area in which they travel does not come within any national airspace.
- Satellites in low Earth orbit have to travel at minimal speeds of about 8 km (5 miles) per second in order not to slip out of their orbit due to the force of gravity. Even very thin air will heat up and slow down a satellite due to friction. The atmosphere will cause such objects traveling below an altitude of approximately 100 km (about 328.000 feet) for any prolonged time to lose speed, fall down and burn up in the process. The lowest point of the orbit (“perigee”) of an artificial satellite will therefore have to be above that altitude.
- Aircraft, deriving their support in the atmosphere from the reactions of the air (see Rule 1 (d)), have not been able to reach – in sustained flight − altitudes where satellites travel. Jet planes have great difficulties exceeding 25 km (about 82.000 feet), while balloons can reach approximately 35 km (about 115.000 feet).[32]
- Because of the decreasing density of the air, winged aircraft have to travel at ever-higher speeds in order to reach higher altitudes. At an altitude of approximately 100 km, a winged aircraft has to travel at about 8 km/sec. This is equal to orbital velocity, which means that the centrifugal force would prevent it from falling down, thus making the concept of winged flight meaningless. While this altitude of ap-proximately 100 km is commonly accepted as distinguishing between aeronautical and astronautical flights, it has not gained universal approval for purposes of international law.
- Ballistic missiles and aircraft that for a limited period of time follow a ballistic trajectory can, in prin-ciple, reach any altitude, including the region between the “highest altitude at which an aircraft can fly” under present technology and “below the lowest possible perigee of an earth satellite in orbit”. It is not settled whether they would violate the airspace of any foreign State because of overflight at such intermediate altitude. Similar problems may arise if future technology makes it possible for some vehicle to hover or fly at such intermediate altitude, or to travel at orbital velocity at such altitude without slowing down and burning due to friction.
- For the purposes of Rule 1 (a), national territory encompasses land, internal waters, archipelagic waters and the territorial sea under the sovereignty of a given State.[33] As far as the territorial sea is concerned, it must be observed that the right of innocent passage – to which all foreign ships are entitled[34] – does not extend to the airspace above the water.
- As regards international straits[35] and archipelagic sea lanes[36], aircraft of all States enjoy the right of transit passage.
- National military manuals treat this subject in different ways and do not therefore throw much light on the question of the highest altitude of the national airspace.[37]
- “Territory not subject to the sovereignty of any State” refers to some parts of Antarctica.[38] In theory, it also refers to the possibility of new emerging islands in the high seas.
- Art. 1 of the Chicago Convention (“Sovereignty”): “The contracting States recognize that every State has complete and exclusive sovereignty over the airspace above its territory.”
- At the time of writing, the world altitude record for air-breathing jet propelled aircraft in controlled horizontal flight is 25.929 meters. Air balloons have reached 34.688 meters.
- Art. 2 of the Chicago Convention (“Territory”): “For the purposes of this Convention the territory of a State shall be deemed to be the land areas and territorial waters adjacent thereto under the sovereignty, suzerainty, protection or mandate of such State.”
- Art. 17 of UNCLOS (“Right of innocent passage”): “Subject to this Convention, ships of all States, whether coastal or land-locked, enjoy the right of innocent passage through the territorial sea.”
- Art. 38 of UNCLOS, see fn. 472.
- Art. 53 of UNCLOS, see fn. 473.
- Para. 217 of the German ZDv: “The dividing line between the airspace of the national territory of a state and outer space shall be drawn where, due to existing physical conditions, the density of the air is small enough to permit the employment of satellites. According to the present state of the art, the minimum flight altitude of satellites ranges between 80 and 110 km above ground level.”
Para. 12.13 of the UK Manual (“Vertical extent of airspace”): “Views differ as to the precise vertical and horizontal extent of airspace. For practical purposes, it can be said that the upper limit to a state’s rights in airspace is above the highest altitude at which an aircraft can fly and below the lowest possible perigee of an earth satellite in orbit. The result is that anything in orbit or beyond can safely be regarded as in outer space.”
Para. 1.10 of the NWP (“Outer space”): “The upper limit or airspace subject to national jurisdiction has not been authoritatively defined by international law. International practice has established that airspace terminates at some point below the point at which artificial satellites can be placed in orbit without free-falling to earth.” - Para. 2 of Art. IV of the Antarctic Treaty: “No acts or activities taking place while the present Treaty is in force shall constitute a basis for asserting, supporting or denying a claim to territorial sovereignty in Antarctica or create any rights of sovereignty in Antarctica. No new claim, or enlargement of an existing claim, to territorial sovereignty in Antarctica shall be asserted while the present Treaty is in force.”
Categories: Section A: Definitions
