In order to provide funds for a system of new major airports near the ten largest cities in the United States, Congress levies a tax of $25 on each airline ticket issued in the United States. The tax applies to every airline ticket, even those for travel that does not originate in, terminate at, or pass through any of those ten large cities. As applied to the issuance in the United States of an airline ticket for travel between two cities that will not be served by any of the new airports, this tax is 
constitutional, because Congress has broad discretion in choosing the subjects of its taxation and may impose taxes on subjects that have no relation to the purpose for which those tax funds will be expended.  constitutional, because an exemption for the issuance of tickets for travel between cities that will not be served by the new airports would deny the purchasers of all other tickets the equal protection of the laws.  unconstitutional, because the burden of the tax outweighs its benefits for passengers whose travel does not originate in, terminate at, or pass through any of the ten largest cities.  unconstitutional, because the tax adversely affects the fundamental right to travel. 