Partly, UAS have been already applied to airlines. During the long trips, pilots depend largely upon the automated operating system. In the case of international airline transportation, it takes a lot of time for taking-off and arriving, so the help of computer programs is need. However, airplane accidents happen constantly despite this support. I think that there are so many unexpected conditions when operating airplanes. So, it seems that operation of automated programs have limitations. Perhaps, the accidents happen because neither human pilots nor computer programs can control unexpected situations. Because of this, it will take much time for the UAS to substitute human controlling.