Who Cares About the Demarcation Line Between Airspace and Outer Space?

Vol. 9, No. 1

Jenifer K. Lamie has her LL.M. in Space, Cyber, and Telecommunications Law from the University of Nebraska College of Law, her J.D. from Vermont Law School, and a Master of International Studies from Otago University. She will join the US Army JAG Corps this summer.

What is the difference between soaring through the skies and launching into the heavens? When traveling from New York to Tokyo, is there a difference between (i) flying at 38,000 feet on a Boeing 777 and (ii) skipping across the suborbital atmosphere in a spacecraft? The answer, of course, is absolutely. But aside from the time saved and turbulence experienced, there is also a legal distinction.

Under long-established principles of international law, “every State has complete and exclusive jurisdiction over the airspace above its territory.”1 Airspace does not extend forever upward. At some point, it becomes outer space. Unlike airspace, which is subject to State sovereignty, outer space is more akin to the high seas because it is not owned by any nation but is instead open for use by all nations. The fundamental treaty governing exploration and use of outer space, commonly known as the Outer Space Treaty, states that outer space “is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means.”2 So, there is a definite distinction between airspace and outer space, and different legal regimes are responsible for each. But where, exactly, does airspace end and outer space begin, or does it really matter?

For example, the geostationary orbit (GSO), which is located above Earth’s equator and appears as a fixed location in the sky, is clearly outer space. In 1976, a group of equatorial nations vainly attempted to assert that their airspace extended to include the GSO.3 However, their claim, known as the Bogota Declaration, was largely rejected by the international community. The general consensus is that the GSO is part of outer space and thus not subject to national sovereignty.

The demarcation between airspace and outer space is not resolved in international treaties on either air law or space law. National laws on the subject are also almost nonexistent.4 Some people argue that the diversification of space activities and the expanding use of outer space necessitate a definitive answer to the demarcation question. The proposals of those favoring a resolution to this question, discussed below, are grounded in science but deviate over which technological criteria to use.5 Although there are benefits to establishing a demarcation line, making such a determination is still premature and would result in an arbitrary distinction.

Two major approaches on how to resolve the demarcation question have been proposed.6 The functional approach frames the issue according to the speed of space objects. Airspace would include the area of the atmosphere which is usable to aircraft, while outer space would begin at the lowest point where spacecraft are traveling fast enough to orbit the Earth. Underlying the functionalist perspective is an emphasis on the purpose or intent of the activity. Thus, the defining fact is not based on geographical considerations but rather on how we use the space, as in the speed of the vehicle and whether or not it is capable of reaching orbit. But framing the issue solely in terms of activities does not help to draw a line between the two physical areas.

In contrast, the spatial approach emphasizes specific scientific parameters, such as gravitational pull and aerodynamics. Proponents of this approach argue that the outer limit of airspace is the altitude, approximately 100 kilometers, where the atmosphere is too thin for an airplane’s wings to generate the aerodynamic lift necessary to sustain flight, known as the Kármán line. Basically, if a vehicle is too high for its wings to keep it aloft, then it is in outer space, and the State cannot assert jurisdiction. Others, however, claim that outer space begins at the lowest possible height that a spacecraft can remain in orbit. Such factors, unfortunately, can change with technological advancements. Thus, to achieve a permanent demarcation that is not vulnerable to the whim of human ingenuity, neither of these two approaches are satisfactory.

The convergence of aircraft and spacecraft technology have further complicated the dialogue and highlighted weaknesses of both the functionalist and the spatial approaches.7 Consider the development of space planes, which are vehicles capable of operating as both aircraft and spacecraft, like Virgin Galactic’s SpaceShipTwo. Virgin Galactic intends to send people into outer space, reaching about 110 kilometers. Using terms appropriate for a functionalist approach, the purpose of their space plane is to reach outer space. However, their planned suborbital flights do not have enough velocity to enter full orbit. Thus, under a spatial approach, where the ability of an object to enter into orbit is a defining characteristic of outer space, the height attained by the space plane would likely not qualify as outer space.

At the dawn of the space age, before manned spaceflight, there was no need to resolve immediately the demarcation issue. The thinking was that when advancements in space activities reached a stage where demarcation was necessary, the international community would come to a consensus. Some claim that we have reached that point, emphasizing the need for unified definitions as the commercial spaceflight industry continues to become more competitive and innovative.8

A case can be made that the commercial spaceflight industry would benefit from a clear distinction in the law that uses a functionalist approach.9 For instance, a definite demarcation would determine whether their vehicle is subject to regulations for aircraft, spacecraft, or both, and which liability regime would govern. Currently, space objects are subject to strict liability under the Liability Convention, the international treaty governing State liability of objects launched into space, while objects traveling through airspace are generally subject to a negligence standard.10 Hypothetically, a demarcation would enable companies to evaluate their risk more accurately, which would encourage additional investment. However, no company has made such arguments, supporting the perspective that making a distinction is still premature.

In addition, many smaller, non-spacefaring nations are for establishing a demarcation line, in contrast to the view of most major space players.11 Because their interests in airspace and outer space hinge on maintaining control over their territory, these nations favor defining a line to ensure activities do not infringe on their sovereignty.12

Though the demarcation line could be established using either the functional or spatial approach, the reality is that both (i) knowledge about the physical limitations of the world and (ii) innovation in space technologies continue to evolve. Thus, notwithstanding the hypothetical concerns of smaller nations over sovereignty or benefits to the commercial industry, a line has not been drawn because it would be premature.

In response to questions posed by the United Nations Committee on Peaceful Uses of Outer Space (COPUOS) on the definition and delimitation of outer space, the US Department of State found no reason to develop definitions of airspace and outer space.13 It argued that the ambiguity in the law did not obstruct the progression of space activities, nor did it threaten state sovereignty. Rather, the State Department voiced a concern that establishing an arbitrary line would be dangerous because it could result in unintended negative consequences. It specifically noted that recent technologies have made it possible for aircraft to fly at higher altitudes and spacecraft to orbit at lower altitudes.

Establishing a line now could very well conflict with future developments in technology. Without a tangible dispute that would lead to useful and less obstructive definitions, there is no justification for choosing a demarcation, and such a decision would be for purely academic rather than practical considerations. Because space-faring nations and the private space industry are disinterested in establishing a demarcation at this time, providing a demarcation risks establishing arbitrary legal definitions of airspace and outer space at a time when they can do more harm than good. u


1. Convention on International Civil Aviation, Dec. 7, 1944, 15 U.N.T.S. 295 (Chicago Convention).

2. Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, Jan. 27, 1967, 18 U.S.T. 2410, 610 U.N.T.S. 205, Art. II (Outer Space Treaty).

3. Declaration of the First Meeting of the Equatorial States, Bogota, 1976, (1978) 6 J. Sp. L. 193–96 (Bogota Declaration).

4. With the exception of Australia, which has gone ahead and codified demarcation at 100 kilometers in their Space Activities Act. See Space Activities Act, 1998 (Austl.).

5. See Gbenga Oduntan, The Never Ending Dispute: Legal Theories on the Spatial Demarcation Boundary Plane Between Airspace and Outer Space, 1 Hertfordshire L. J. 64 (2003).

6. See generally Frans G. Von der Dunk, The Sky Is the Limit—But Where Does It End?, in Proceedings of the Forty-Eighth Colloquium on the Law of Outer Space (2006), 84–94, available at http://digitalcommons.unl.edu/spacelaw/34; Oduntan, supra note 5.

7. Oduntan, supra note 5, at 74; see also the Virgin Galactic website for more information about their spaceships, http://www.virgingalactic.com.

8. See Committee on Peaceful Uses of Outer Space, Report of the Legal Subcommittee on Its Fiftieth Session, U.N. Doc. A/AC.105/990 (Apr. 20, 2011).

9. See von der Dunk, supra note 6 at 88 (explaining how the private sector prefers a functionalist approach that includes all their activities in one regime while governments prefer a spatial approach due to their interest protecting their borders).

10. Katherine M. Gorove, Delimitation of Outer Space and the Aerospace Object—Where Is the Law?, 28 J. Space L. 11, 13 (2000); Convention on International Liability for Damage Caused by Space Objects, Mar. 29, 1972, 24 U.S.T. 2389, 961 U.N.T.S. 187 (Liability Convention); Chicago Convention, supra note 2.

11. With the exception of, for example, Russia, which has proposed to establish a boundary at around 100 kilometers. Gorove, supra note 10, at 15–16.

12. Gorove, supra note 10, at 16.

13. U.S. Statement, Definition and Delimitation of Outer Space and the Character and Utilization of the Geostationary Orbit, Legal Subcommittee of the United Nations Committee on the Peaceful Uses of Outer Space at its 40th Session in Vienna from April, available at http://www.state.gov/s/l/22718.htm.


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