Sean Seyer’s monograph Sovereign Skies seeks to make an important argument relevant to our own time: “international conventions, agreements, and regulatory regimes affect national policy formation even in the absence of official adherence” (189). In other words, non-signatories are still compelled to comply with an international framework, even though they lack the ability to influence it. The framework in question is the Convention Relating to the Regulation of Aerial Navigation, adopted in 1919 and commonly known as the Paris Convention. Regulating transborder aviation, it established national sovereignty over airspace as its main principle and defined the conditions under which the aircraft of one nation could enter another state’s territory. Even though a U.S. delegation took part in negotiating the Paris Convention, Congress never ratified the agreement, owing to its association with the League of Nations and concerns that, if signed, it would restrict U.S. foreign aviation while opening the door to European competitors in the Western Hemisphere.
Seyer studies how civil aviation policy emerged in the United States during the first decade following World War I. In doing so, he focuses on the “interconnectivity among domestic and foreign considerations,” showing, on the one hand, how policymakers engaged with the international framework (188). On the other hand, following debates among government officials, interest groups, and federal agencies, he argues that U.S. aviation policy was significantly shaped by a domestic struggle over who held sovereignty over the airspace: the states or the federal government. Seyer demonstrates that federal authority over American skies was not clearly established from the outset but had to be enforced and developed over time, with the Paris Convention playing an important role in this process.
Chapter one outlines how questions of federal versus state authority had already emerged in relation to earlier forms of transportation. Beginning in the nineteenth century, steamship and railroad transportation were gradually brought under federal authority, primarily driven by public safety concerns. In contrast, automobility remained at the state level—underscoring that it was far from certain that aviation would automatically fall under federal jurisdiction. In chapters two, three, and four, Seyer details the process that eventually led to the federal regulation of aviation. He first examines how, in the immediate aftermath of World War I, the Paris Convention emerged as a key issue for the development of the United States’ own aviation policy. The planned cross-border air traffic with Canada required a mutual legal agreement, and as a result, a federal agency, the National Advisory Committee for Aeronautics, as well as an industry group, the Manufacturers Aircraft Association, pushed for U.S. participation in the new air convention. The international character of aviation was increasingly used to justify calls for federal, rather than state-based, regulation.
Heavily publicized accidents underscored the need for federal involvement as they were attributed to a lack of uniform standards. Still, debates continued over the proper administrative framework for federal aviation oversight: should it be through a separate Air Department or an interdepartmental board? Civil aviation ultimately fell under the Department of Commerce’s authority. The Air Commerce Act of 1926 established federal control over aviation—even for intrastate flight—and authorized the Department of Commerce to set safety standards. Crucially, the legislation followed the principles established in Paris. Seyer advances this point in chapter five, once again focusing on the years leading up to the Air Commerce Act of 1926. He details how U.S. policymakers aligned domestic provisions with the system established in Paris in order to make American commercial aviation compatible with international commerce. Using tables to illustrate and compare the articles of various regulatory frameworks, he convincingly demonstrates how provisions concerning traffic rules, aircraft, and pilot qualification in different rulesets—the Underwriters Laboratories insurance system (1920), the American Aeronautical Safety Code (1925), and the Air Commerce Regulations of December 1926—often copied the ideas and language of the 1919 Paris Convention.
The final chapter revisits the question of why the United States, despite taking considerable inspiration from the Paris Convention, ultimately chose not to ratify it. Security and defense concerns, as well as the extension of the Monroe Doctrine into the air, were central to this decision. Seyer shows that the U.S. State Department sought to compensate for what it saw as the convention’s shortcomings by pursuing a new air agreement that “needed to remain as unobstructive as possible to US interests, prevent European aerial competition in the Western Hemisphere, and allow the United States to restrict foreign access to the all-important Panama Canal Zone” (161). Within the Pan American Union—an organization promoting cooperation among the states of the Americas—a new framework for aerial navigation in the Western Hemisphere was adopted: the Havana Convention of 1928. Mostly following Wesley Phillips Newton’s earlier analysis of U.S. aviation diplomacy in the Western Hemisphere in The Perilous Sky (1978), Seyer shows that several Latin American nations, spearheaded by Colombia, opposed measures which they saw as U.S. imperialist aims, which is why the new convention ultimately fell short of the State Department’s goals.
Seyer’s book convincingly situates U.S. aviation policy within a global context. Through meticulous archival research, he carefully reconstructs the debates and tensions across different branches of the U.S. government, as well as among key interest groups, effectively supporting his claim that “the 1919 air convention created an international regime … that Americans could not ignore” (128). One notable weakness of this otherwise compelling book is its structure: while the main text is concise at 189 pages, it suffers from some repetition and chronological jumps between chapters. At the same time, much relevant information is relegated to the endnotes. This criticism notwithstanding, Seyer successfully demonstrates how U.S. air regulations unfolded in dialogue with an emerging international aerial regime, influencing aviation even on the interstate and intrastate levels. This insight applies not only to aviation policy but also to U.S. policymaking more broadly during a period when the country remained formally absent from the key international institution, the League of Nations. Seyer’s study of civil aviation thus offers an important and fresh perspective on how interwar globalization still profoundly shaped U.S. domestic policymaking.
