Challenges in developing lightweight alloys for aerospace applications include: achieving high specific strength while maintaining low density, ensuring thermal stability at elevated temperatures, improving fatigue and fracture resistance under cyclic loading, enhancing corrosion and stress corrosion cracking resistance, overcoming processing and manufacturability difficulties (machinability, weldability, scalability), reducing dependency on costly or scarce alloying elements (e.g., Scandium, rare earths), and addressing compatibility issues with composite materials in hybrid aerospace structures.