Sovereign Skies: The Origins of American Civil Aviation Policy. By Sean Seyer. Baltimore: Johns Hopkins University Press, 2021. 312 pp. + 15 b&w illus. Hardcover, 67. 95. ISBN: 978-1-4214-4053-8.

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