Rationale for revision Co-processing of non-conventional feedstocks is a viable means of introducing greater amounts of renewable content in aviation turbine fuel. Currently, co-hydroprocessing of non-conventional feedstocks in refineries is limited to triglycerides, fatty acids and fatty acid esters or Fischer-Tropsch liquids, as currently permitted in Annex A1 of ASTM D1655. Synthetic hydrocarbons derived from previously hydroprocessed fatty acids and fatty acid esters are another potential co-processing feedstock that offers a means to greater renewable content in refined jet fuel. These synthetic hydrocarbons, when fractionated, are chemically identical to and indistinguishable from kerosene fractions derived from conventional feedstocks. At a minimum, co-processing of synthetic hydrocarbons from previously hydroprocessed esters and fatty acids in the feed to a refinery unit will require fractionation for the finished jet fuel to meet the requirements already stipulated in Tables 1 and A1.1. In order to control the impact of trace materials that may be found in synthetic hydrocarbons derived from previously hydroprocessed and biologically-sourced esters and fatty acids, a minimum purchase specification requirement has been included with reference to EN 15940. Additionally, the finished, co-processed synthesized kerosene will demonstrate compliance with both ASTM D1655 Table A1.1 and ASTM D7566 Table A2.2 as additional co-processing quality controls.