Guo Xiao is a Ph.D. candidate of Beihang University. His main research interest is aircraft trajectory optimization and hardware-in- loop simulation technique.Corresponding author. Tel.: + 86 10 82338481. E-mail addresses: guoxiao@ase.buaa.edu.cn (X. Guo), Zhu Ming received his M.S. and Ph.D. degrees in mechanical engi- neering in Beihang University and then become a teacher there. His main research interests are automatic and aircraft control system. zm_buaa@ 163.com (M. Zhu).