The increasing demand forSupercapacitors sustainableElectric aviation and efficient aviation has driven the exploration of advanced energy storage systemsEnergy storage system that can complement or replace conventional technologies. Among these, supercapacitorsSupercapacitors have attracted significant attention due to their high power density, rapid charge–discharge capability, and long cycle life. This chapter provides an overview of the fundamental principles of supercapacitorsSupercapacitors, including electric double-layer capacitors, pseudocapacitors, and hybrid supercapacitorsSupercapacitors, highlighting the underlying mechanisms that enable their unique performance characteristics. Building on this foundation, the chapter explores the role of supercapacitorsSupercapacitors in aviation, with emphasis on their applications as standalone storage devices and as key components in hybrid systemsHybrid systems integrated with fuel cellsFuel cells and lithium-ion batteriesLithium-ion battery. This chapter also presents a review of the state-of-the-art in electrically powered propulsion (EPP) for aircraftAircraft, emphasizing how supercapacitorSupercapacitors-based solutions can contribute to improved efficiency, reduced emissions, and enhanced reliability. By presenting a structured progression from fundamental principles to real-world applications and emerging propulsion concepts, this work aims to underline the pivotal role of supercapacitorsSupercapacitors in advancing the transition toward more sustainable aviation.