send a letter by airmail

• 寄一封航空信

send a letter by airmail的用法和样例：

例句

1. What is the postage for an air letter?
   寄一封航空信的邮费要多少？
2. An airmail letter from here to Shanghai should not take more than two days.
   从这儿寄一封航空信到上海的时间不会超过两天。