1. School of Air Transport, Transportation, Logistics and Air Law, Korea Aerospace University, Gyeonggi-Do, Korea, yhlee@kau.ac.kr
2. Graduate School, Korea Aerospace University, Gyeonggi-Do, 412-791, Korea
3. Division of Aeronautical Studies, Han Seo University, Chungchungname-Do, Korea, pilot@hanseo.ac.kr