NASA and its industry partners are taking unmanned aircraft systems closer to operating in harmony with other aircraft in the national airspace. The technology and procedures developed during a nearly decade-long program has been assisting the Federal Aviation Administration (FAA), develop the rules for certification of unmanned aircraft to safely coexist with other air traffic. The goal is to enable new commercial and public service opportunities, such as real-time surveillance of fires, infrastructure inspections for pipelines and medical transportation in the future. NASA began its Unmanned Aircraft Systems (UAS) Integration in the National Airspace System (NAS) Project in 2011. Work since then has included multiple simulation efforts and six specific flight tests series that focused on validating these simulations and supporting the development of minimum operational performance standards (MOPS) for Detect and Avoid (DAA) systems.