In the case of United Air Lines, Inc. v. Mahin, Director of Department of Revenue et al., 1972, United Airlines challenged an Illinois state law that imposed a tax on the sale of aviation fuel. The airline argued that this tax was in violation of federal laws governing interstate commerce and air travel. However, the Supreme Court ruled against United Airlines by upholding the constitutionality of Illinois' sales tax on jet fuel purchased within its borders for use in interstate flights. The court found no conflict between state taxation and federal regulation or policy regarding aviation fuels; it also rejected arguments about multiple taxation burdens due to different states’ taxes as speculative and not supported by evidence from this particular case.

In the dissenting opinion for United Air Lines, Inc. v. Mahin, Justice Douglas argued that Illinois' tax on jet fuel unfairly burdened interstate commerce and was therefore unconstitutional under the Commerce Clause of the U.S. Constitution. He contended that while a state has the right to levy taxes for services provided, such as airport facilities in this case, it should not be able to do so in a way that discriminates against or unduly burdens interstate commerce. In his view, taxing airlines based on their purchase of jet fuel within Illinois disproportionately affected out-of-state businesses who were simply passing through but had no choice but to refuel there due to technical necessities rather than any benefit derived from being in Illinois per se.