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Intrastate airlines in the United States were air carriers operating solely within a single US state and taking other steps to minimize participation in interstate commerce, thus enabling them to escape tight federal economic airline regulation prior to US airline deregulation in 1979. These intrastate carriers therefore amounted to a small unregulated, or less regulated, sector within what was otherwise then a tightly regulated industry. As detailed below, flying within the geographic boundaries of a single state was a necessary but not sufficient condition to qualify as an intrastate carrier.
Despite providing a small proportion of US airline capacity, the success of these airlines, in particular Pacific Southwest Airlines (PSA), and Southwest Airlines, played a major role in the advent of US airline deregulation and thus airline deregulation globally, and the subsequent growth of low cost and ultra-low cost carriers. Further, US airline deregulation was merely the first in a wave of general economic deregulation by the federal government, eventually extending to railroads, trucking, energy, communications and finance.