Sustainable Aviation Fuel (SAF) is considered an effective mid-term solution for achieving carbon neutrality in aviation. Since the chemical composition of SAF differs from that of conventional Jet A fuel, a detailed understanding of its combustion characteristics is essential to design and adequately operate practical aero-engine combustors. The previous researchers have majorly focused on the steady combustion and emissions properties of SAF [e.g. 1,2]. Limited studies have been conducted to gain a deeper insight into the key mechanism of SAF that affects the combustion instabilities [e.g. 3-5]. Despite these advances, a systematic understanding remains lacking, and the underlying physics remains unclear. In the present study, Large-Eddy Simulations (LESs) are conducted to investigate combustion instabilities occurring in a realistic spray flame combustor. The spray flames of both Jet A and SAF are considered to elucidate the effect of fuel composition differences on the characteristics of combustion instabilities. The target combustor and combustion conditions are the same as those in Tachibana et al. [6], who previously investigated self-excited oscillations of Jet A in a swirling spray combustor at elevated pressure at JAXA (Japan Aerospace Exploration Agency) through both the experiments and high-fidelity LES at the time. The results demonstrate that the present LES reproduces the experimentally observed self-excited oscillations for Jet A reported in Tachibana et al. [6], and that the characteristics of combustion instabilities differ between