Aircraft and aircraft parts are taxable. A project that is not completed is still taxable on the total consideration of the aircraft parts or project. If the aircraft is not completed, consumer use tax will be due on any future purchases or importations of aircraft parts even if consumer use tax was previously paid on the unfinished project.
If you import an aircraft kit that has been completed, tax would be due on the fair market value of the completed assembled aircraft. Credit may be given for any tax previously paid with proof of the taxes paid.