The International Civil Operations of Unmanned Aircraft Systems under Air Law explores the current legal and regulatory frameworks comprehensively from the perspective of how they may facilitate the routine and cross-border operations of unmanned aircraft systems (UAS). While the International Civil Aviation Organization is working to amend and create new Standards and Recommended Practices for the operation of UAS on cross-border flights, Member States have already produced regulations that facilitate the integration and operation of the aircraft within their national airspace. This situation is causing to subvert the attempt to develop uniform and harmonised normative for UAS for international flight operations. The increasing operations of UAS have increased the safety and security concerns on manned aviation, and hence there is an escalating need to adopt a comprehensive regulatory framework for the operation of UAS aimed at safe and efficient integration. The author, a well-known air law practitioner and diplomat, identifies the legal challenges and proposes sound, well-informed measures to tackle such challenges.