1. I sent my friend an air letter to let them know about my trip to Japan.
我给我的朋友寄了一封航空信，告诉他们我去日本的旅行。

2. Air letters are a quick and efficient way to communicate with people overseas.
航空信是与海外人士快速有效沟通的方式。

3. My grandmother used to send me air letters when I was studying abroad.
我在国外留学时，奶奶经常给我寄航空信。

4. The air letter arrived at its destination in just a few days.
航空信在几天内就到达了目的地。

5. I prefer to use air letters when sending important documents internationally.
在国际上寄送重要文件时，我更喜欢使用航空信。

6. The air letter was securely sealed to protect its contents during transit.
航空信被安全密封，以保护其内容在运输过程中。