Why A Commercial Jet Flying At 35,000 Feet Is Actually Traveling Through Airspace That Doesn't Legally Exist

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Victoria Agronsky

Published May 23, 2026, 2:00 PM EDT

Experienced ICAO English Language Proficiency Instructor for pilots and ATCOs and conference interpreter who is passionate about facilitating effective communication within aviation-related businesses. Possess a deep understanding of the aviation industry, including aviation regulations, terminology, and industry-specific communication protocols. Has been working at numerous airshows across Europe since 2014. Being an ultralight pilot in her free time, she also promotes safety and efficiency in aviation operations.

Based in Italy and Malta

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Commercial aviation is one of the most tightly regulated industries on Earth. Every flight level, navigation procedure, maintenance interval, and crew certification requirement is governed by an intricate network of international agreements and national regulations. Every day, thousands of jet airliners cruise across the Atlantic at 35,000 feet inside a legal framework that contains a remarkable contradiction: no one has ever fully agreed where sovereign airspace actually ends.<br>That creates a strange reality for modern aviation. A Boeing 777 crossing the North Atlantic or an Airbus A350 flying between Europe and Asia operates in a zone where international law becomes surprisingly vague. The deeper one looks into aviation law, the clearer it becomes that some of the world’s busiest flight corridors are governed less by precise legal definition and more by decades of operational compromise. The system works extraordinarily well in practice, but legally speaking, parts of the sky remain unresolved territory.

International Aviation Law Never Defined The Top Of Airspace

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The foundation of modern aviation law is the 1944 Chicago Convention, which established the rules governing global civil aviation. The treaty clearly states that every country has “complete and exclusive sovereignty” over the airspace above its territory. However, the agreement never explained where that airspace actually stops. That omission still exists today. According to Encyclopedia Britannica’s overview of air law, no internationally accepted altitude has ever been legally established as the boundary between sovereign airspace and outer space.<br>At first glance, this may sound like an issue relevant only to astronauts or the Air Force. Commercial aircraft cruise nowhere near space, with most long-haul flights operating between FL290 and FL410. Yet the absence of a legal upper boundary creates a fundamental gap in international law. States possess sovereignty over airspace, while outer space is legally free from sovereignty claims, but the transition point between those two regimes has never been formally defined.<br>The most widely recognized practical boundary is the Kármán Line, positioned at 100 kilometers above sea level. Engineers and aerospace organizations frequently use this altitude because aerodynamic flight becomes nearly impossible beyond it. However, the Kármán Line has no binding legal status. ThomasNet’s analysis of the Kármán Line explains that it is more of a scientific convention than an internationally ratified rule. The United States complicates matters further because agencies, including NASA and the FAA, recognize space as beginning at 50 miles (about 80 kilometers) above Earth’s surface.<br>That creates a legally ambiguous band between 80 and 100 kilometers. International law does not definitively classify that zone as sovereign airspace or outer space. At commercial cruise altitude, this ambiguity changes little operationally, but it reveals a broader truth: the legal architecture of the sky above every airline flight remains incomplete.

The Outer Space Treaty Left The Biggest Question Unanswered

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Credit: Wikimedia Commons

The ambiguity became even more significant during the space race of the 1950s and 1960s. As satellites and crewed missions became technologically feasible, governments needed a legal framework governing activity beyond Earth. The result was the 1967 Outer Space Treaty, which declared outer space to be free for exploration by all states and prohibited national sovereignty claims beyond Earth.<br>However, the treaty deliberately avoided defining where outer space begins. According to the House of Commons Library’s research briefing on space regulation, decades of international discussion have not produced a consensus on delimitation. Countries understand that any fixed boundary would affect national defense systems, missile trajectories, reconnaissance operations, commercial...