乘務員告訴你：坐飛機這麼花錢最虧！Things you should never buy on planes, according to flight attendant
但是不要等上了飛機才要求升艙，乘務員通常沒有這麼高的權限。Most banks or shopping malls have currency exchanges with steadier rates if you remember before your flight. And if you forget， just get enough money for a taxi into the city and go to a local bank.