復數：airport taxes

1. Before boarding the flight, passengers are required to pay the airport tax at the check-in counter.
   在登機之前，乘客需要在登機柜臺支付機場稅。
2. Many travelers are unaware that the ticket price does not include the airport tax, which can be quite substantial.
   許多旅客并不知道機票價格不包括機場稅，這筆費用可能相當可觀。