Purpose – This study aims to evaluate the feasibility of using grape seed oil methyl ester as an alternative to Jet A-1 in gas turbine engines without requiring any modifications, in terms of thrust, emissions, thermal efficiency and fuel consumption. For this purpose, experiments were performed by producing 2.5%, 5%, 10% volume methyl ester reinforced biojet fuels with transesterification technique and analyzed comparatively with Jet A-1 results. Design/methodology/approach – To investigate this issue, an experimental set that can measure using a real mini jet engine was designed and operated at different engine speeds (taxi, approach, climbing and take off) under different operating conditions. Findings – The experimental results were compared with Jet-A1 results and similar results were found. Overall, it has been demonstrated that B5 fuel can be an alternative to Jet A-1 in terms of thrust, emissions, thermal efficiency and fuel consumption, and can be used in gas turbine engines without requiring any modifications. Practical implications – The thrust, emission and other data of all fuels were measured depending on the engine speed and changes compared to the control sample were determined. The production of grape seed oil biojet fuel was carried out through transesterification. The biojet was mixed with kerosene at ratios of 2.5%, 5% and 10%. Originality/value – The novelty of this work comes from obtaining biojet from grape seed oil methyl ester and using it in real jet engines.