In 1944, when the war was coming to an end, President Roosevelt invited the nations of the world to a conference in Chicago with a view to establishing a global regime for the burgeoning commercial aviation sector that would flourish after the war. The President said in his invitation: “I do not believe that the world today can afford to wait several years for its air communications. There is no reason why it should. Increasingly, the airplanes will be in existence…”. At the present time, this message could be applied to commercial space transport with just a change of words to adapt to the increasingly developing space tourism sector.

It would not be true to say that ICAO has hitherto not addressed the issue of space transport. The ICAO Assembly, at its 16th Session held in Buenos Aires from 3 to 26 September 1968, adopted Resolution A 16-11 (Participation by ICAO in Programmes for the Exploration and Use of Outer Space). Recognizing that the events of the past years were of great interest to ICAO, since many of the activities affect matters falling within ICAO’s competence under the provisions of the Chicago Convention, and that the United Nations had recognized the competence of certain specialized agencies that could perform various useful functions and such interest had to be welcomed and encouraged, the Assembly resolved that ICAO be responsible for stating the position of international civil aviation on all related outer space matters and for stating international civil aviation’s particular requirements in respect of application of space technology.

Commercial space flight is here, and it is a foregone conclusion that it will take off in earnest within the next few years. The issue is whether we are prepared with the necessary legislative and infrastructural base to launch these flights in sustained progression. Unlike the Chicago Convention of 1944 which was adopted at the Chicago Conference pursuant to the initiative of President Roosevelt, there is no multilateral legal instrument that provides comprehensively for commercial space transportation. When commercial air transport was in its incipient stages the world community took just over a month to develop, draft, and adopt the Chicago Convention that comprehensively provided for technical and commercial regulation. This treaty still serves air transport well.

We continue to use and explore outer space, take pictures, calculate trajectories of planets and determine who owns the moon and what the purpose of outer space exploration is. An added dimension is the use of aerospace in terrestrial transportation where an aerospace plane will take off as an aircraft, go into orbit, enter the atmosphere using the Earth’s orbit into its destination, cutting the travel time significantly. It is said that by using this method, air travel time can be reduced drastically. For instance, a journey by air between Los Angeles and Sydney, which would now take 14–16 h by conventional air travel, could take 2 h or less.

It is well known that the newest and most expensive mode of transportation is commercial space travel which offers high-end suborbital flights to space tourists. Some consider it an extension of air travel, mostly on the basis that a spacecraft that operates suborbital flights would have to traverse airspace to go beyond it. This has encouraged some academics to suggest that this area of travel can easily be accommodated within the existing air transport regime, by incorporating the various safety principles that would be adopted for commercial space travel within existing treaty provisions with some adaptation and modification. Although there may be some commonality in both air travel and outer space travel, on the basis that a vehicle operating suborbital flights would go through airspace, it would be both unwise and impracticable to move a space travel regime lock stock and barrel into the existing air transport regime.

Given that a spacecraft traverses airspace before it goes into outer space, one would have to have a clear, internationally accepted definition of outer space. No multilateral treaty currently applicable to space transportation or the exploration and exploitation of outer space resources has this definition. This is both disconcerting and unsettling in an age where complex and advanced space exploration has been taking place well over 5 decades, with a man stepping on the moon in 1969. In this context, neither is airspace defined, although commercial air travel has been regulated for the past 67 years.

Given that a spacecraft traverses airspace before it goes into outer space, one would have to have a clear, internationally accepted definition of outer space. No multilateral treaty currently applicable to space transportation or the exploration and exploitation of outer space resources has this definition.¹ A State, according to the 1933 definition in the Montevideo Convention, has to be composed inter alia of a “defined geographic area”, which is controlled by its populace. Therefore, it goes without saying that a State has sovereignty over its defined land area. Judge Huber noted in the Island of Palmas Case² that:

Sovereignty in the relations between States signifies independence. Independence in relation to a portion of the globe is the right to exercise therein, to the exclusion of any other State, the function of a State. The development of the national organization of States during the last few centuries and, as a corollary, the development of international law, have established this principle of exclusive competence of the State in regard to its own territory in such a way as to make it the point of departure in settling most questions that concern international relations. Sovereignty in relation to a portion of the surface of the globe is the legal condition necessary for the inclusion of such portion in the territory of any particular State.³

As for territorial waters adjacent thereto (which is considered as included in the territory of a State) this has also been recognized by multilateral treaty in Article 3 of the Convention on the United Nations Law of the Sea (UNCLOS) which stipulates that “Every State has the right to establish the breadth of its territorial sea up to a limit not exceeding 12 nautical miles, measured from baselines determined in accordance with UNCLOS”. Therefore, Article 2 of the Chicago Convention and its definition of “territory” is consistent with the aforementioned established principles of international law.

As per principles of public international law, air space does not constitute the territory of a State and should not be confused with the word “territory”. The reason is that the dimensions of airspace have not been defined either by treaty or by customary recognition (Australia has a domestic law which recognizes that airspace goes up to 100 km over its land and adjacent sea territory. Other instances of definition of airspace are hitherto unknown). Therefore States cannot ipso facto claim sovereignty over the airspace above their territory unless such is recognized by treaty and this is what the Chicago Convention does in Article 1.

The Permanent Court of International Justice, when requested for a definition of “air space” in the 1933 Eastern Greenland’s Case, ⁴ was of the view that the natural meaning of the term was its geographical meaning. The most fundamental assumption that one could reach from this conclusion is that air space is essentially geo-physical, meaning that it is space where air is found. Simplistically put, “air space” has been considered as going upwards into space from the territorial boundaries of a State and downwards to the centre of the Earth, in the shape of an inverted cone.

Recognition by States of their sovereignty over their airspace (as stated in Article 1 of the Chicago Convention) inevitably presupposes that this rule has already been entrenched in the annals of air law in an earlier instrument. The Convention Relating to the Regulation of Aerial Navigation signed by 26 States on 13 October 1919 established that the High Contracting Parties recognize that every Power has complete and exclusive sovereignty over the airspace above its territory.

As for outer space, at the time of writing, the aerospace community was considering such issues as sub-orbital flights and space tourism, both of which could further blur the boundaries between air space and outer space, while raising other issues of topical interest. As already mentioned, so far, there has not been a universally accepted definition distinguishing air space and outer space. Some years ago, when the legalities of an aerospace plane, which is a hypersonic single stage to orbit reusable vehicle that horizontally takes off and lands on a conventional runway were considered, it was thought that the transit through near space which is involved is incidental to the main transit which takes place within the airspace. Generally, the aerospace plane, which will be constructed with the use of aeronautical and space technologies and would be capable, and, indeed, required to fly both in airspace and outer space, would bring to bear the need to consider the applicability of and appropriateness of laws relating to the space plane’s activities. It will be subject to the sovereignty of the State whose airspace it is in. This is an incontrovertible fact which need not be stated since any object within the airspace of a territorial State would indeed be subject to that State’s sovereignty.

The United Nations Committee on the Peaceful Uses of Outer Space (UNCOPUOS), which is the UN forum where technical and legal aspects of space activities with global impact are considered, has discussed the issue of the definition and delimitation of outer space from 1962 and no definite conclusion has been reached so far in this regard. In this connection, it is of interest to note that the Legal Subcommittee of UNCOPUOS, through its Working Group on Matters Relating to the Definition and Delimitation of Outer Space, has been considering possible legal issues with regard to aerospace objects. A questionnaire thereon was circulated to all U.N. Member States. A compilation of the replies received and an analytical summary of such replies, as well as a historical summary on the consideration of the question on the definition and delimitation of outer space, may be found on the OOSA website.⁵

As debated for decades in the framework of UNCOPUOS, it may be questioned whether the vertical limit of airspace would be critical to determine the scope of applicability of air law as opposed to international space law conventions (spatialist approach), or whether the type of activities at issue would determine which law should apply (functionalist approach) to sub orbital flights. The latter school of thought submits that flights which would be passing merely in transit through (sub)orbital space in the course of an earth-to-earth transportation would be in air space and therefore remain subject to principles of air law.

A sub-orbital flight is a flight up to a very high altitude which does not involve sending the vehicle into orbit. ‘Sub-orbital trajectory’, which a sub orbital flight would follow, is defined in the legislation of the United States as “The intentional flight path of a launch vehicle, re-entry vehicle, or any portion thereof, whose vacuum instantaneous impact point does not leave the surface of the Earth.”

In 2004, SpaceShipOne was the first private vehicle to complete two sub-orbital flights within 2 weeks carrying weight equivalent to three human adults up to about 62.5 miles (100 km) to win the Ansari X Prize. It was carried during 1 h by an aeroplane up to nearly 50,000 feet (9.5 miles) from where it was released into a glide and then propelled vertically for 80 s by a rocket motor to an altitude of more than 62 miles at apogee, reaching a speed over Mach 3. Then falling back to return to earth, it re-entered the atmosphere and glided during 15–20 min before landing back on the runway of departure.

SpaceShipOne, strictly speaking, does not operate as an aeroplane or even as an aircraft during the ballistic portion of the flight while it is not supported by the reactions of the air, even though some degree of aerodynamic control exists throughout the trajectory from launch altitude until the craft enters the upper reaches of the atmosphere where the air density is no longer sufficient for aerodynamic flight. After apogee, during re-entry into the atmosphere the vehicle transitions to unpowered aerodynamic (gliding) flight for the return to earth. Consequently, depending upon some design and operational aspects, it could be considered operating as an aircraft in flight during this latter portion of the journey.

Therefore, such vehicles could fulfil the principal elements in the definition of aircraft and be used as such during a portion of their flights, but they offer some characteristics of a rocket as well. It is likely that other vehicles engaged in the future in such sub-orbital flights would similarly be of an hybrid nature, taking into account that developments to come may lead to a range of designs, some of which could be more clearly classified as aircraft. Should sub-orbital vehicles be considered (primarily) as aircraft, when engaged in international air navigation, consequences would follow under the Chicago Convention, mainly in terms of registration, airworthiness certification, pilot licensing and operational requirements (unless they are otherwise classified as State aircraft under Article 3 of the Convention).

Plans have been announced by Virgin Galactic for the development of a fleet of five sub-orbital vehicles to carry paying passengers, six per vehicle; it planned that the first of these will be ready for commercial operations in 2008 at the earliest. There are indications that at least one other company is planning to offer rival sub-orbital flights.

Manned and unmanned sub-orbital flights have been undertaken to test spacecraft and launch vehicles intended for later orbital flight, but some vehicles have been designed exclusively to reach space sub-orbitally: manned vehicles such as the X-15 and SpaceShipOne, and unmanned ones such as ICBMs and sounding rockets.Sub-orbital tourist flights will initially focus on attaining the altitude required to qualify as reaching space. The flight path will probably be either vertical or very steep, with the spacecraft landing back at its take-off site.