The creation of alternative fuels to reduce CO2 emissions in the aeronautical sector necessitates the determination of their safety properties, among which are their Flammability Limits. Synthesized Iso-Paraffins (SIP) are blending components that have already been approved for blending with traditional aviation fuel by up to 10 vol%. Therefore, this manuscript is aimed at experimentally determining the Lower Flammability Limit (LFL) of SIP, jet fuel and mixtures of 10% (F10) and 50% (F50) in mass of SIP at atmospheric and reduced pressures with air. For this purpose, an experimental bench was built in accordance with American Society for Testing and Materials, ASTM E681. The LFL of the samples was initially determined at a pressure of 101.3 kPa and high temperatures. Afterward, the LFL of samples was determined at reduced pressures, i.e. 80, 60, 40 and 20 kPa, and also high temperatures. For this analysis, 316 tests were performed. For a better understanding of the experimental results, additional material is attached, presenting the temperatures and the volumes used in carrying out each test. Finally, adjustment equations based on the experimental results of this manuscript for SIP, jet fuel, and their mixtures, were presented as a function of temperature and atmospheric pressure.