In October 1975, Montreal—Mirabel International Airport opened to the travelling public. This article examines why the federal government and its partners embraced megaproject ideology to build Mirabel, how these multiple institutions formulated and negotiated their airport vision, and its subsequent impact on the local land and people. It argues that politicians and planners broke new ground with Mirabel, fashioning it as a site of and for mass aeromobility that would be much more than a new airport. Influenced by postwar pro-growth discourse, as well as developments at the city and provincial level, they settled on an unprecedentedly large airport that could expand well into the future jet age. To make this vision a reality, however, Mirabel’s boosters overlooked or deliberately disregarded the socio-environmental effects of an airport megaproject, choosing to impose a distinct aeromobile landscape that altered the character and identity of the local area. In the process, they endorsed a technocratic idea of development that accelerated jet age sprawl as modernized airports like Mirabel became more spatially dominant and disruptive within natural and built environments.