AbstractUnmanned aircraft system (UAS) operations are growing in numbers, type of applications, technical complexity and regulatory challenges. National aviation regulatory authorities are engaged in coming up with regulatory and policy framework for seamless integration and operation of UAS in civil airspace. Integration of UAS into civil airspace is a complex and challenging System of Systems (SoS) engineering problem involving multiple stakeholders, complex airborne and ground systems / subsystems, processes, regulatory frameworks, etc. Recent research and developments in SoS engineering provide tools for representing, modelling and analysis of complex SoSs which would help in taking design decisions and risk mitigation. In this paper, the problem of integrating UAS into controlled civil airspace is analyzed from the SoS engineering stand point. The key system elements involved in the problem and their relationship and interactions are modelled as a SoS. The relationship between the technical challenges associated with the key SoS elements and the standard SoS dimensional properties is established. An approach for developing an architecture model of the proposed SoS is discussed.