Helpful Links
Here are some links to other websites:
World Airport Path Finder Find the direct distance between airports for the SIFL calculation.
FAA Aircraft Registry The FAA website for registration and certification of aircraft and airmen.
The Digital Daily The Internal Revenue Service website. This site has all the IRS forms and instructions and publications discussing the income and transportation tax rules applicable to aircraft.
Multistate Tax Commission The Multistate Tax Commission website.  This has a copy of the latest Multistate Exemption Certificate which can be used to claim the sales tax resale exemption in most States.