The "Interstate Ferry Fairness Act" significantly broadens the scope of the Federal Ferry Boat Program by amending title 23, United States Code. This legislation makes privately owned or majority-privately owned ferries and their terminal facilities eligible for federal funding, a change from the previous requirement for public ownership. The primary goal is to facilitate federal participation in the construction or purchase of these assets, particularly for critical transportation links between adjoining states. Under the revised provisions, federal participation is permitted for majority publicly owned entities if they provide substantial public benefits, and for privately or majority-privately owned entities if they operate between two adjoining states and offer substantial public benefits or meet surface transportation needs. The bill also outlines a new fare structure for privately owned interstate ferries, allowing them to charge amounts covering operational costs, maintenance, debt service, and a Secretary-determined reasonable rate of return. Conforming amendments ensure that these newly eligible entities can also access funding through the surface transportation block grant program, with the changes taking effect one year after enactment for certain program eligibilities.