The Delimitation between Airspace and Outer Space

For this new Space Law article on Space Legal Issues, let’s study the Delimitation between Airspace and Outer Space. The issue of where airspace ends and outer space begins has been debated since the 1950s. This legal issue is important since Air Law and Space Law are governed by vastly different legal regimes. The delimitation debate among publicists and among states demonstrates the lack of clarity in a line between air and space. In the absence of clarity, we yield to the default legal position; that is, follow the rule and not the exception.

In the legal literature, there exist many good ideas on delimitation, based on many different concerns such as Airspace and Outer Space traffic control, insurance, commercial development (in particular space tourism and hypersonic transportation), pure science, and a host of other notions. Any one of these concerns may be a firm basis on which a regime of delimitation can be founded (with the remaining concerns adjusting their regulations and practices to whatever line is determined). But, as yet, there is no clear state consensus as to a line or the primary foundation upon which any such delimitation should be based.

The constant evolution of technology gave rise to concrete case studies relevant to the long-standing debate on the definition and delimitation of outer space. The regimes of both Air Law and of Space Law were developed at a time when the technology for Earth-to-Earth aerospace movements did not yet exist. Thus, there is not yet a unified or integrated regime of aerospace law. Moreover, there is significant inconsistency between the regimes of Air Law and Space Law.

Air Law

Let’s note that Air Law applies to airspace and aircrafts. States enjoy “complete and exclusive sovereignty” over their territorial air space. The Convention on International Civil Aviation (also known as Chicago Convention) states that “Every state has complete and exclusive sovereignty in the airspace above its territory”. It also declares that “Territory includes the land areas and territorial waters adjacent thereto”. Air Law imposes liability on the airline, or the aircraft operator and requires States to certify and register aircraft, and environmental standards. Air Law requires States to regulate safety, navigation, and security; it also States requires to regulate noise and emissions.

Article 3 of the 1944 Chicago Convention adds that “No state aircraft of a contracting State shall fly over the territory of another State or land thereon without authorization by special agreement or otherwise, and in accordance with terms thereof”. Article 6 of the 1944 Chicago Convention declares that “No scheduled international air service may be operated over or into the territory of a contracting State, except with the special permission or other authorization of that State, and in accordance with the terms of such permission or authorization”.

Article 12 of the 1944 Chicago Convention states that “Each contracting State undertakes to adopt measures to insure that every aircraft flying over or manoeuvring within its territory and that every aircraft carrying its nationality mark, wherever such aircraft may be, shall comply with the rules and regulations relating to the flight and manoeuvre of aircraft there in force. Each contracting State undertakes to keep its own regulations in these respects uniform, to the greatest possible extent, with those established from time to time under this Convention. Over the high seas, the rules in force shall be those established under this Convention. Each contracting State”.

Space Law

Let’s note that Space Law applies to outer space and space objects. State sovereignty over outer space is prohibited and Space Law imposes liability and oversight responsibility upon the State; it also creates an international registration regime. There is yet no universal safety, navigation or security standards in outer space.

Article II of the 1967 Outer Space Treaty affirms that “Outer space, including the Moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means”.

The Delimitation between Airspace and Outer Space

Neither “Airspace” nor “Outer Space” are defined in the relevant treaties. Development of suborbital flights would benefit from the delineation of where Airspace ends and Outer Space begins. Commercial suborbital spaceflights use vehicles that reach an altitude of approximately one hundred kilometres, the theoretical line proposed by Theodore von Kármán to separate the fields of aeronautics and astronautics. This line has been recognised by the Fédération aéronautique internationale. Australia has also adopted one hundred kilometres as the jurisdictional limit of its national Airspace. But setting the boundary of territorial air space that high would restrict launches to the discretion of the underlying State.

Commercial and military interests have begun to develop operating systems in near-space (at an altitude of roughly twenty to eighty kilometres). Such systems include suborbital vehicles, stratospheric balloons, pseudo-satellites and high-altitude drones. Operations in near-space are a potential threat for air traffic beneath and for the public on ground, in case of failures or malfunctions. They are also a threat for space outbound and returning traffic.

The following operational boundaries exist between aviation and outer space: one hundred and sixty kilometres (lowest practical operating orbit for satellites), one hundred and twenty kilometres (re-entry threshold for space systems), or eighteen kilometres (upper limit of civil aviation traffic).

Predictability of outcomes would be enhanced if the question of whether Air Law, or Space Law, or a new regime of “Aerospace Law” applied to suborbital flights. Commercial development of space would be facilitated by clarity, stability and predictability of law. Uniformity of law will improve the market’s interest in investment in space transportation, and the insurance industry’s ability to assess and price risk. Delineation of which legal regime will enhance the margin of safety for aircraft, spacecraft and aerospace vehicles operating in all three zones.

Spatialism and Functionalism

Two primary schools of thought have emerged on the issue of air and space delimitation: spatialism and functionalism. Spatialism essentially argues for a fixed line, at a set altitude, for the division of airspace and outer space. Under a strict spatialist analysis, if a craft, regardless of its nature and capabilities, is below the line, it is in airspace; when it is above the line, it is in outer space. Conversely, functionalism focuses on the nature of the craft in question. If it serves outer space functions, outer space law applies wherever it is operating; if it is an aircraft, airspace law applies to its flight. In effect, this “approach would render it unnecessary to solve the theoretical dispute whether there is a boundary between airspace and outer space and where it should be located”.

Of course, even within these broad schools are more particular and inconsistent theories of delimitation. Further, some thinkers and space-faring states believe there is no need to decide the issue. The emergence of hybrid aerospace vehicles challenges these theories and compounds the lack of consensus. Their ability to operate in either airspace or outer space, straddling any line established between the two, can make their control and regulation ambiguous and inconsistent if spatially-based. Further, their function is novel. On any given flight, they may operate both as an aircraft and a spacecraft.

As one description of the functional approach explained, “one way to answer the question as to which regime of law applies is to ask what type of vehicle is being considered”. But, the extant legal regimes present just a binary option: only airspace or outer space law can apply; there is presently no established regime for aerospace vehicles. The existing theories provide no definitive or universal guidance for the operation of aerospace vehicles, particularly in the grey area between air and space law.

While there is no clear edge of the airspace or no precise lower border for outer space, these domains are universally acknowledged as both existing and possessing a fairly straightforward legal regime (vis-a-vis sovereignty and state vehicles). Some national laws might evolve in the upcoming years into a state practice and become opinio juris. We hope these questions will be discussed at the Legal Subcommittee of the United Nations’ Committee on the Peaceful Uses of Outer Space (COPUOS). That is what can be said about the Delimitation between Airspace and Outer Space.