2-1. Airspace Defined:

a. Scope of Chapter. This chapter surveys a wide variety of general international law topics relevant to the law of armed conflict. It explains basic legal concepts relevant to airspace including airspace over national territory, territorial seas, and high seas. Related concepts of identification zones and outer space are discussed. Legal rules relevant to control of airspace and outerspace are covered. The basic legal concepts regarding access of military aircraft to airspace, both during armed conflict and during peacetime, are surveyed. Civil aircraft are discussed, as appropriate.

b. Historic Roots of Definition of Airspace. Until the advent, in the 20th century, of reliable craft capable of carrying men or materials through the air, little public consideration was given to the question of sovereignty, ownership or control over "airspace." It was assumed that sovereignty over the land implied sovereignty over all superjacent airspace. To the extent that a state claimed sovereignty or other rights of control over littoral waters as "territorial" seas, the surface rules were presumed equally applicable to the air above. The space immediately above the earth's surface and constituting the atmosphere has since been regulated in accordance with these concepts. With the development in the second half of the 20th century of craft not dependent upon atmosphere to provide lift, and able to navigate at great speeds high above the earth's surface, a wholly separate regime has developed for "outer space." No fixed boundary between the two has been recognized under international law to date.

c. Airspace Over National Territory, Internal Waters and Territorial Seas. The upper geographic limits of "airspace" are still undefined by international law. Neverthe

less, an extensive body of law is applicable to the zone next to the earth characterized by the presence of atmosphere. 2 This zone is here referred to as airspace. The legal status of airspace is essentially identical to that of the national territory, internal waters and territorial seas below it. The rule was embodied in the first multilateral international agreement on the subject: the 1919 Paris Convention Relating to the Regulation of Aerial Navigation, and has been followed in all subsequent international agreements. The Convention purports to express the rule for all states, including those not parties to it. Although the United States did not ratify the 1919 Convention, this country nevertheless adopted the principle in its first Air Commerce Act of 1926 and all successor laws. 3 Territorial sovereignty over the airspace includes all of the attributes of sovereign control, including the rights to regulate, and ultimately prevent access, exit or transit of both personnel and aircraft, whether or not manned.

d. Innocent Passage. The Convention on the Territorial Sea and the Contiguous Zone codified international law on "innocent passage" through the territorial sea. Innocent passage is the right of all ships, including military vessels, to traverse the territorial sea of other states provided passage is "not prejudicial to the peace, good order or security of the coastal state."4 No comparable right has been recognized for aircraft through airspace over the territorial sea or other territory of another state.

e. Airspace Over the High Seas. Article 1 of the 1958 Convention on the High Seas, to which more than 50 nations are parties, defines the "high seas" as

all parts of the sea that are not included in the territorial sea or in the internal waters of a State. 5

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This definition does not establish the geographic width of the "territorial sea." Nor does international agreement on the width of the territorial sea now exist. The United States was among the first to establish and has generally adhered to the view that the appropriate width is 3 miles from the low water mark on the shore. Many nations claim up to 12 miles, and some others claim 200 miles. Whatever the outer boundary of the territorial sea, the rule that has evolved for airspace above the high seas has flowed from the strictly territorial concepts applicable to airspace. Thus, as sovereignty may not be exercised over the high seas, so assertions of sovereignty in the form of controlling or denying access, exit or transit are improper in the airspace above the high seas and above territory unclaimed by any sovereign (to the extent it exists). This does not mean that a sovereign is denied all right of action in the airspace above the high seas. On the high seas sovereigns may act in self defense and may engage in any other reasonable activity that does not interfere with the rights of others also freely to use the high seas. The airspace above the high seas is subject to the same regime. As summarized in Article 2 of the 1958 Convention on the High Seas,

The high seas being open to all nations, no State may validly purport to subject any part of them to its sovereignty. Freedom of the high seas is exercised inter alia, both for coastal and noncoastal States [through]

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(4) Freedom to fly over the high seas. Airspace that is not national airspace may be referred to as international airspace. The international airspace includes all airspace above the high seas, above unclaimed areas, and over other areas which by agreement have in some respect been internationalized. 8

f. Absence of "Contiguous Zones" in Airspace. The 1958 Convention on the Territorial Sea and the Contiguous Zone9 codified international practice under which states are permitted to establish relatively narrow

"contiguous zones" of the high seas immediately adjacent to their territorial seas, within which they may exercise certain controls without claiming sovereignty over such areas. Under the Convention, the contiguous zone is limited to a width of 12 miles from the coast, within which the coastal state may, according to Art. 24(1), establish such controls as are

necessary to:

(a) Prevent infringement of its customs, fiscal, immigration or sanitary regulations within its territory or territorial sea;

(b) Punish infringement of the above regulations committed within its territory or territorial sea.

Security controls are not among those enumerated in the Convention. As the contiguous zone is a part of the high seas, the coastal state may not prevent passage of warships or otherwise impede access, exit or transit. This is always subject to the right of every nation to act in self defense and to use the seas for observation and similar purposes that do not interfere with the equal rights of use by others.

The concept of the "contiguous zone" is not recognized in airspace. Accordingly. airspace must be considered either entirely within the territorial control of a sovereign if superjacent to territory or territorial sea or entirely outside the control of any sovereign when above the high seas.

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g. Air Defense Identification Zones. The United States is among the countries in the world that have established "air defense identification zones" (ADIZ) in the airspace above the high seas adjacent to their coasts and above their territory and territorial seas. Civil aircraft on a course to penetrate United States airspace are required to identify themselves upon entry into the zone. This requirement is based on the right of every state to establish conditions and procedures for entry into its airspace. 12 State aircraft on a course to penetrate United States airspace may be requested to identify themselves. and failing voluntary identification may be identified by intercept aircraft or otherwise

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as appropriate. An air defense identification zone does not constitute a claim of sovereignty over airspace above the high seas. Such a zone is merely a reference point for initiation of identification procedures for aircraft on a course to penetrate national airspace. In addition to air defense identification zones, "warning zones" have been created from time to time. 13

h. Differences Between "Airspace" and "Outerspace." Although the upper limit of airspace has not yet been authoritatively defined, international practice since the orbiting of Sputnik I in 1957, has established that it ends below the lowest altitude at which artificial satellites can be placed in orbit without free-falling to earth. Under both customary and treaty law, a right of passage concept for orbiting satellites and manned spacecraft has developed 14 subject to the outer space regime discussed in paragraph 23, this publication. As with the airspace above the high seas, prohibition on the exercise of sovereign controls in outer space does not prevent any sovereign either from acting in its self defense against hostile acts in that domain (such as the orbiting of weapons) or in using the domain for nonhostile acts of its own (such as surveillance). 15

2-2. Control of Airspace:

a. Sovereign State's Complete Control Over National Airspace. It is a firmly established rule of international law that the sovereign over particular territory and territorial seas has absolute control over the superjacent airspace. This airspace is referred to as "national airspace." From this principle flow the following generally accepted corollaries:

(1) No aircraft may enter national airspace without prior permission, either specific or based upon prior general agreement;

(2) Each aircraft entering national airspace must identify itself;

(3) Each aircraft entering national airspace must obey all reasonable orders of the territorial state, including orders to land, to turn back or to fly a prescribed course

(unless prevented by distress or force majeure);

(4) Control by the territorial sovereign of aircraft intruding national airspace cannot expose the craft or occupants to unreasonable dangers. Thus, in time of peace, intruding aircraft known to be harmless to the security or other appropriate interests of the territorial state may not be attacked even if they disobey orders to land. On the other hand, if the intruder's intentions are unknown and cannot reasonably be ascertained, after disregard of appropriate warnings, the intruder may be forced to land or attacked if it refuses to obey;

(5) Intruding aircraft may be given immunity from the consequences of intrusion if it is genuinely based on distress or force majeure. Because of the difficulty of determining if distress is genuine, such circumstances as response to requests for identification, location of the aircraft in relation to military or other installations requiring protection, character of the aircraft, its equipment, and crew are relevant to a determination of whether immunity should be accorded. If immunity is not properly claimed, the crew and aircraft of the intruder are subject to the civil and criminal law of the territory intruded. 16

b. International Agreements Affecting Control of National Airspace. The basic international agreement affecting control of national airspace is the Convention on International Civil Aviation of 1944 (Chicago). It confirms the rule that absent permission aircraft of one state may not enter the national airspace of another. Permission for military aircraft to enter the airspace of another sovereign can never be presumed. If the right to enter is based upon the consent of the territorial sovereign, there must be some expression of agreement found.

Numerous bilateral agreements relating to overflight by military aircraft have been concluded by the United States. Usually, United States military overflight, landing and take off rights are included in military base rights or mutual defense agreements. 17 Article 43 of the United Nations Charter further

obligates members to assure "rights of passage" through national airspace for military aircraft engaged in actions undertaken pursuant to decisions of the Security Council.

2-3. Control of Outerspace:

a. Historic Development of Different Regime. Since access to outer space has been a recent phenomenon, traditional practices have not played as significant a role in the development of a legal regime as was the case with airspace. Shortly after the Soviet Union first orbited an artificial satellite in 1957, the United States adopted the National Aeronautics and Space Act of 1958 expressing this country's goal that activities in outer space should be devoted to peaceful purposes for the benefit of all mankind. However, Congress did direct that adequate provisions be made in space activities for the welfare and security of the United States. The DOD was given specific responsibility for space activities pertaining to or primarily associated with the development of weapons systems, military operations or defense of the United States including research and development. Resolutions of the United Nations General Assembly unanimously adopted in 1961 and 1963, were fully consistent with the goal of peaceful purposes and culminated in the Space Treaty of 1967. This treaty and others have established for outer space legal rules that have few terrestrial counterparts and which provide for general access, shared information and peaceful

b. International Agreements:

(1) The Space Treaty. The principal international agreement applicable to outer space is the Space Treaty of 1967, to which over 65 states are parties including the two states most heavily involved, the United States and the Soviet Union. Under the treaty, all parties are assured freedom of, access to, and exploration of, all regions of outer space, the moon, and other celestial bodies; and freedom to use space and the celestial bodies on the basis of equality and in accordance with international law, including the right to conduct scientific investiga

tions. The treaty prohibits the appropriation as national territory of outer space, the moon, or any celestial body and the orbiting, emplacement or testing of nuclear weapons or weapons of mass destruction. The establishment of military bases or the conduct of military maneuvers and interference with the peaceful use of space, the moon, or other celestial bodies by others is prohibited. Finally, the treaty imposes obligations on parties to render assistance to astronauts and to accept liability for damages from its space activities, to return space objects found on its territory and astronauts who land there in distress, and to avoid activities that would be harmful to the environment of the earth or of celestial bodies.

(2) Other treaties. The Nuclear Test Ban Treaty of 1963 bans the testing of nuclear weapons in outer space. Separate agreements on the rescue and return of astronauts and liability for objects launched into space elaborate some of the provisions of the Space Treaty on those subjects. 19 Work is continuing in the UN on more detailed agreements relating to registration, direct broadcasting from satellites and other issues.

24. Military Aircraft:

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a. Definition of "Aircraft." The definitional annex to the Chicago Convention of 1944 defines "aircraft," as a machine that "can derive support in the atmosphere from the reactions of the air." It thus includes both heavier than air and lighter than air objects, but appears to exclude objects more properly viewed as projectiles which do not derive support from the reactions with the air, such as rockets. On the other hand, the definition does not require the existence of any crew; pilotless craft can be regarded as "aircraft." Domestic US legislation is more broadly drawn; the Federal Aviation Act defines "aircraft" as "any contrivance now known or hereafter invented, used, or designed for navigation of or flight in air." 49 U.S.C. §1301(5) (1970).

b. Nationality of Aircraft. Aircraft, like ships, have the nationality of their country of