A provision of the Airport and Airway Improvement Act of 1982, 49 U.S.C. App. 1513(d)(1), prohibits the imposition of discriminatory state or local property taxes on air carriers. However, 1513(d)(3) provides that the prohibition does not apply to any "in lieu tax which is wholly utilized for airport and aeronautical purposes." The South Dakota Airline Flight Property Tax, enacted in 1961, is imposed on air carriers on the basis of the value of their aircraft and provides for allocation of the taxes to the airports used by the carriers, and for use of the taxes exclusively by the airports for airport purposes. This tax, which is centrally assessed, was an exception from the general state scheme of local property tax assessment at the county level. In 1978 the State exempted from ad valorem taxation all personal property that was locally rather than centrally assessed. Appellant airline companies paid their flight property taxes in 1983 under protest, unsuccessfully sought refunds from appropriate county and state authorities