Upgrading a Fischer-Tropsch synthesis product by separating a 350.degree. to 850.degree. F product fraction thereof into a 650.degree. F minus fraction and a 650.degree. F plus fraction; separating the 650.degree. F minus fraction to provide a more narrow 350.degree. to 650.degree. F fraction; combining the 650.degree. F plus fraction with a portion of the 350.degree. to 650.degree. F fraction to form a wide boiling range feed material; contacting this formed wide boiling range feed material, together with hydrogen, with a special catalyst comprising a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least 12 and a constraint index of 1 to 12, at a temperature of about 500.degree. to 800.degree. F, a hydrogen partial pressure of about 100 to 800 psia and a space velocity of about 0.5 to 5 LHSV to produce a converted product thereof separating the zeolite conversion product to recover a 350.degree. F minus fraction from a 350.degree. F plus fractions; and separating the 350.degree. F plus fraction to recover a 350.degree. to 450.degree. F jet fuel fraction having a freeze point of less than about -58.degree. F.