航空客运订票系统
通过此系统可以实现如下功能：
录入：可以录入航班情况
查询：可以查询某个航线的情况；可以输入起飞抵达城市，查询飞机航班情况；
订票：可以订票，如果该航班已经无票，可以提供相关可选择航班；
退票：可退票，退票后修改相关数据文件；(Airline passenger booking system

The following functions can be realized through this system:

Entry: can enter the flight situation

Enquiries: you can inquire about the situation of a certain airline; you can enter and fly to the city to inquire about the flight condition.

Booking: you can book tickets. If the flight is already free, you can provide related optional flights.

Refund: refund, refund after modification of relevant data files;)