The increasing urgency to address global warming has highlighted the need to explore alternative fuels for the transport sector, a significant contributor to carbonemissions. Hydrogen and ammonia have emerged as promising candidates, each with distinct advantages and challenges. Hydrogen boasts high reactivity and beneficial cooling properties but suffers from low volumetric density and storage difficulties. Conversely, ammonia offers better infrastructure compatibility and higher volumetric density but has low flammability. This study investigates computationally hydrogen/ammonia flames under sub-atmospheric conditions pertinent to high altitude aviation, focusing on laminar flame dynamics. One-dimensional simulations of freely propagating laminar flames were conducted using the PREMIX software and analyzed with computational singular perturbation (CSP) tools to elucidate the flame structure and dynamics. Results reveal that hydrogen/ammonia blends improve flame speed and stability compared to pure ammonia, especially under lean conditions. CSP analysis identified key reactions driving flame behavior, highlighting differences in chemical dynamics between hydrogen and ammonia. The findings underscore the potential of hydrogen/ammonia blends in aviation applications, particularly for high-altitude relight scenarios, and provide insights into optimizing fuel mixtures for enhanced performance. Further research is needed to validate these findings under varied conditions and explore practical implementation strategies.