说明：  该系统需要实现以下功能： (1) 订票：若该航次余票数大于等于客订票数，则在该航次的乘客表（按乘客姓氏字母词典顺序排列）中， 插入订票乘客的信息项，并修改该航次有关数据，否则给出相应提示信息； (2) 退票：若退票数小于该乘客原订票数，则在相应的乘客表中找到该乘客项，修改该航次及乘客表中有关数据。 当由于退票使得该乘客的订票数为零时，要从乘客表中撤销该乘客项；否则给出相应的提示信息； (3) 将某航次的余票数恢复初值为该航次的最大客票数； (4) 显示：显示该机场各航次班机的售票情况。
(The system needs to achieve the following functions: (1) Booking: If the voyage than the number of votes greater than or equal passenger booking, cruise passengers in the table (by passengers alphabetical dictionary order) in Items of information into the booking of passengers, and modify the data of the voyage, or give the appropriate message (2) Refund: If the refund is less than the number of votes of the original passengers, passengers in the corresponding entry in the table to find the passengers, the voyage and the passengers to modify the data in the table. When the refund makes the number of passengers booking is zero, from the passenger list of passengers in the revocation of the item otherwise give the corresponding message (3) the recovery of a voyage of more than the initial value for votes in the largest cruise ticket number (4): Displays of the voyage of the airport flight ticket sales.)