民航系统功能：能给客户提供订票、退票的功能，还能浏览航班航线信息（如航班号、航线、飞行时间及成员订额）和查询航班信息-CAD system functions : give customers booking, a refund of the function, can browse flight route information (such as flight number, route, time of flight and members of the amount set), and