Something’s in the Air: ‘Spy Balloons,’ High-Altitude Objects, and Vertical Sovereignty

Something’s in the Air: ‘Spy Balloons,’ High-Altitude Objects, and Vertical Sovereignty

Ian Johnson

On January 28th, 2023, the United States identified an object entering United States’ airspace near Alaska’s Aleutian Islands.[1] By Tuesday, January 31st, the object had drifted through western Canada and re-entered US territory near Idaho.[2] By the next day, February 1st, the object had made it further east, above Montana.[3]  This grabbed the attention of the Department of Defense, since Billings, Montana is home to Malmstrom Air Force Base, which is one of the few bases in the country that operate and maintain intercontinental ballistic missiles.[4] The object seemed to hover for some time around Billings,[5] and it was at this point that Pentagon officials began identifying the object as a balloon used for spying employed by the Chinese government.[6] The balloon continued west across the continental United States before it was shot down off of the coast of South Carolina on February 4th.[7]

The ‘spy balloon’ saga not only caused a media frenzy in the United States and prompted increased tensions between the US and China with Secretary of State Anthony Blinken canceling a planned trip to Beijing[8] and the Commerce Department announcing sanctions against six Chinese aerospace companies that were identified as supporting China’s international surveillance program,[9] but it has also reignited a decades-long debate surrounding the murky international legal status of high-altitude objects and the vertical sovereignty of states.

One of the major attempts to achieve some level of international cooperation with respect to airspace was the Convention on International Civil Aviation that took place in Chicago in December 1944 (“the Chicago Convention”).[10] The Chicago Convention accomplished several things. It established that all states have absolute sovereignty and control over the airspace above their territory,[11] including the area above its territorial waters.[12] The Chicago Convention also provided no right of ‘innocent passage,’ meaning that international air travel is only allowed through special permission of the state in which you wish to travel.[13] Since the Chicago Convention in 1944, 193 countries have signed onto the agreement.[14] China signed onto the agreement originally in 1944, and the People’s Republic of China subsequently recognized the agreement in 1974.[15]

While the Chicago Convention did do a lot to lay the groundwork for international cooperation in reference to air travel, there are also questions that it did not provide an answer to that are causing problems now (re: ‘Spy Balloon’) and will continue to cause problems further down the road. A major oversight in the Chicago Convention is that it does not define the term “airspace” or its upper limit.[16] Legal scholars have attempted to derive a definition of “airspace” by using the history of the Chicago Convention. It has been argued that the Chicago Convention deals only with flight instruments that derive support in the atmosphere from reactions of the air—like balloons and airplanes—not with objects like rockets, satellites, and other craft that can move without atmospheric support.[17] This definition would have placed the upper limit of “airspace” of around 140,000 feet in 1956, which was the highest flight by any unmanned balloon.[18] Still, no common definition of “airspace” or its upper limit has been adopted internationally. This has led to nations defining their sovereign vertical airspace differently, which has created the need for thousands of bilateral and multilateral agreements which are necessary for international air service.[19] For example, Australia has declared their vertical sovereignty to extend to an upper limit of 60,000 feet, and Germany does not define the upper limit of their airspace.[20] In 1957, the USSR asserted that their vertical sovereignty extends to an “unlimited height,” and the United Kingdom has defined their vertical upper limit to be “at least as high as any aircraft can fly.”[21]

The US position on vertical state sovereignty has remained ambiguous. The US has claimed complete sovereignty over its airspace, but, like other nations, has also not defined an exact upper limit.[22] Somewhat ironically, in 1956, amid a controversy surrounding US high-altitude surveillance balloons being spotted over the USSR, Secretary of State John Dulles explained that the U.S. has a right to send balloons at a certain height anywhere around the globe.[23] Though, when asked for the approximate height that a balloon leaves the area of state sovereignty Dulles responded, “I just can’t answer that question.”[24]

The Chinese ‘spy balloon’ was shot down at an altitude of about 60,000 feet,[25] which by most international standards was within the sovereign vertical air space of the United States.[26] However, the ‘spy balloon’ saga is a reminder of the international legal ambiguities that will continue to arise as technological advancements push objects higher and higher into the sky. Under UN law, outer space is free for exploration and use by all states and sheltered from any claim of state sovereignty.[27] However, there is no international agreement as to where state sovereignty over vertical air space ends and where free outer space begins.[28] As things like high-flying drone technology continues to advance, commercial rocket and space exploration companies begin to proliferate, and high-altitude state surveillance programs continue to evolve and expand, international legal questions over who controls the skies will inevitably arise. The international community needs an update to the Chicago Convention that provides a real definition to the term “airspace” and establishes a clear line between state-controlled airspace and free outer space.


[1] Helene Cooper & Edward Wong, China’s Spy Balloon Drifted for 7 Days Across the U.S.: A Timeline, N.Y. Times (Feb. 4, 2023),

[2] Id.

[3] Id.

[4] Id.

[5] Chinese Spy Balloon Over US is Weather Device says Beijing, BBC News (Feb. 3, 2023),

[6] Cooper & Wong, supra note 1.

[7] Id.

[8] Edward Wong & Julian E. Barnes, Chinese Balloon Had Tools to Collect Electronic Communications, U.S. Says, N.Y. Times (Feb. 9, 2023),

[9] Chelsey Cox & Christina Wilkie, U.S. sanctions six Chinese tech companies for supporting spy balloon programs, CNBC Politics (Feb. 10, 2023, 4:52 PM),

[10] Convention on International Civil Aviation, Dec. 7, 1944, art. 43, 61 Stat. 1180, 15 U.N.T.S. 295.

[11] Id. at art. 1.

[12] Id. at art. 2.

[13] Id. at art. 6.

[14] Convention on International Civil Aviation Signed at Chicago on 7 December 1944 (Status), Int’l. Civ. Aviation Org., (last visited Feb. 14, 2023).

[15] Id.

[16] Dean N. Reinhardt, The Vertical Limit of State Sovereignty (Jun. 2005) (L.L.M thesis, McGill University),,law%20is%20growing%20in%20importance.

[17] John Cobb Copper, Legal Problems of Upper Space, 27 J. Air L. & Commerce 308, 311 (1956).

[18] Id.

[19] Reinhardt, supra note 16, at 13.

[20] Id. at 18-20.

[21] Id.

[22] Id. at 20-23.

[23] Id. at 21.

[24] Id.

[25] Jim Garamone, F-22 Safely Shoots Down Chinese Spy Balloon Off South Carolina Coast, DOD News (Feb. 4, 2023),

[26] Reinhardt, supra note 16, at 18-24.

[27]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, art. I, 18 U.S.T. 2410, 610.

[28] Reinhardt, supra note 16, at ii.