In City of Dallas v. Southwest Airlines Co., 371 F. Supp. 1015 (N.D. Tex. 1973), aff'd, 494 F.2d 773 (5th Cir. 1974) municipalities sought to exclude an intrastate airline from operating at a city-owned airport. The court determined that the legislature vested the Texas Aeronautics Commission (TAC) with the authority to determine and provide for the public convenience and necessity of the citizens of the entire state regarding all aspects of intrastate air service. See Southwest Airlines, 371 F. Supp. at 1032-33. The municipalities' efforts to regulate the airline impinged on TAC's jurisdiction and was therefore invalid. See Southwest Airlines, 371 F. Supp. at 1033. Moreover, TAC had ordered the airline not to discontinue service at any airport. The municipalities' attempt to exclude the airline's operations at the airport was in direct conflict with TAC's order. See Southwest Airlines, 371 F. Supp. at 1033-34.