How about September 13th? 那9月13日的呢?
It's fully booked at the moment. 现在都订满了。
I'm very sorry, but the flight is completely booked. 实在抱歉,那趟班机全部订满了。
I can put you on a waiting list if you would like. 如果你愿意,我可以把你排在等候名单上。
I'll just check to see if there have been any cancellation. 我会来查一下是否有取消预订的。