On May 22, 1922, Herbert Frahy was briefly the most talked-about man in Washington, D.C. Defying officials at Bolling Field, Frahy took off in a Curtiss JN-4 biplane and flew to the National Mall, where he provided an impromptu air show for the crowd of thousands gathered to dedicate the newly completed Lincoln Memorial. Although it earned him widespread condemnation—including from President Warren G. Harding, whose ceremonial speech was interrupted by the spectacle—Frahy’s dangerous stunt had broken no laws, and the young pilot suffered little more than a slap on the wrist.

Such episodes enliven Sean Seyer’s fascinating account of how a collection of individuals and interest groups transformed the “open and lawless frontier” of early American aviation into “a primary arena for the modern regulatory state” (p. 3). Seyer argues that three factors shaped early U.S. aviation policy: the uniqueness of the airplane’s three-dimensional movement, concerns about constitutional federalism, and a desire to align domestic regulations with emerging international principles. Previous scholars have viewed interwar civil aviation policy as either a by-product of federal subsidies promoting flight or the realization of top-down progressive regulatory visions. Seyer’s study distinguishes itself from these interpretations by highlighting the contributions that mid-level civil servants and industry representatives made to U.S. aviation regulations, and the influence that foreign ideas about “air sovereignty” had on the shape those policies took. More broadly speaking, Seyer contends that the “borderless” nature of flight—and, by extension, other technologies that “[blur] the line between the domestic and international spheres”—prompted reevaluations of U.S. federal power and promoted the adoption of internal rules that were compatible with newly formulated international principles (p. 189).

Seyer opens his study by situating the airplane within the nation’s efforts to regulate new modes of transportation starting in the nineteenth century. In the case of steamboats and railroads, the federal government gradually assumed regulatory control through judicial and legislative action based on expansive readings of the Commerce Clause. Automobiles, on the other hand, fell under the purview of individual states and municipalities, which imposed a dizzying array of often conflicting rules. Deeming the latter approach unsuitable for the dynamic technology of flight, aviation proponents were divided over the constitutional basis for its regulation. Instead, they turned for guidance to the international arena, where victorious Allied policymakers had begun defining new rules and procedures in the 1919 Convention Relating to the Regulation of Aerial Navigation. Though doomed by its association with the ill-fated League of Nations, the Convention came to play an outsized role in American aviation policy in the years that followed. Canadian and British adoption further elevated the international agreement’s status among U.S. policymakers as cross-border flight depended on reciprocity in aerial rules.

Having agreed upon the need for strong federal policy, industry, government, and military representatives spent the first half of the 1920s addressing the question of what the new air regulations would look like. Seyer ably guides the reader through this laborious process, beginning with debates between those who felt a unified Air Department should administer federal policy and others who wanted to separate military and civil aviation. Regulatory proponents likewise continued to struggle with how to justify proposed legislation, meeting resistance from segregationist lawmakers who saw reliance on the Commerce Clause as a possible intrusion on states’ rights. Passed against the backdrop of a growing number of aviation accidents, the Air Commerce Act of 1926 was a compromise solution that subjected all aircraft to a unified set of federal regulations while leaving non-commercial registration and licensing requirements to the states. The authors of the Act leaned heavily on the 1919 Convention for guidance, ensuring that subsequent U.S. air rules complemented those of countries that signed the earlier agreement. This alignment with international principles also blunted subsequent U.S. efforts to secure a hemispheric air convention, much to the dismay of American foreign policymakers.

Based upon an impressive array of sources, Sovereign Skies makes a convincing case for the interdependence of domestic aviation policy and international regulations. Seyer’s focus on the yeoman’s work of policymaking—an unglamorous process that required intensive study of technical subjects, consensus-building among diverse constituencies, and tedious refinement of final rules—is particularly welcome given the tendency of many aviation historians to gravitate toward accounts of great people, companies, or inventions. Given how central the debate on federalism was to these backroom conversations, more details on the opposition presented by states’ rights legislators would likely have further strengthened Seyer’s argument. This minor quibble aside, Sovereign Skies is a thoroughly readable and well-argued addition to the body of writing on American civil aviation.