Oregon Revised Statutes Revenue and Taxation § 319.417

(1) On or after October 3, 1989, and on or before July 15 of each year thereafter, the Oregon Department of Administrative Services, after consultation with the Department of Transportation and the Director of the Oregon Department of Aviation shall estimate, using a methodology approved by the Oregon Transportation Commission, the amount of the motor vehicle fuel tax imposed under ORS 319.010 to 319.430 during the preceding fiscal year with respect to motor vehicle fuel purchased and used in operating aircraft engines and upon which the full tax for motor vehicle fuel has been paid. The estimate shall be reduced by the amount of any refunds actually paid on motor vehicle fuel, excluding those paid on aviation gasoline or jet fuel, during the preceding fiscal year pursuant to ORS 319.330 (1).

(2) The Oregon Department of Administrative Services shall certify the amount of the estimate made under subsection (1) of this section to the Department of Transportation, the Director of the Oregon Department of Aviation and the State Treasurer. Thereupon, the amount of the estimate shall be transferred from the Department of Transportation Driver and Motor Vehicle Suspense Account to the State Aviation Account and is continuously appropriated to the Oregon Department of Aviation to carry out the purposes of ORS chapters 835, 836 and 837.