A change to ASTM D7566 Annex 5 to include isobutene as an approved starting material, being a process intermediate in the Gevo ATJ pathway. The ASTM specification D7566 Annex 5 defines a synthetic paraffinic kerosene (SPK) blend stock produced from isobutanol or ethanol. To produce alcohol-to-jet synthetic paraffinic kerosene (ATJ-SPK), the alcohol is dehydrated to produce isobutene or ethylene, followed by oligomerization, hydrogenation and fractionation. A new process developed by Global Bioenergies (GBE) closely resembles Gevos isobutanol to jet fuel pathway, in which microorganisms directly produce isobutene during the fermentation followed by the same set of upgrading steps (oligomerization, hydrogenation and fractionation). The resulting jet fuel is similar in composition and characteristics as isobutanol based jet fuel. It is therefore proposed to include isobutene as an approved starting material in the ATJ-SPK Annex 5. Also, since isobutene is the dehydrated equivalent of isobutanol, we propose to make the dehydration step only applicable when using an alcohol as starting material.