A UAV is defined as a powered, aerial vehicle that does not carry a human operator, and can fly autonomously or be piloted remotely. UAV operations have increased dramatically during the past several years in both the public and private sectors. The utilization of UAV and the activities of diverse widening, now the challenge was how to operate and integrate UAV safely in the NAS. The purpose of this study is to look around the trend for operability of Smart UAV in the NAS and to provide its implications and the future direction of integrated operating airspace focusing on U.S. where R&D and demand of UAV are the most in the world.