“系好安全带”常见的英文表达有：
Fasten your seat belt：这是最常用、最直接的说法，“fasten”有“系牢、扣紧”的意思，“seat belt”即“安全带” 。例如：Please fasten your seat belt before the plane takes off.（飞机起飞前请系好安全带。）
Buckle up your seat belt：“buckle up”意思是“扣上（安全带等）的搭扣” ，和“fasten your seat belt”意思相近。例如：The pilot reminded passengers to buckle up their seat belts.（飞行员提醒乘客系好安全带。 ）
Put on your seat belt：这种表达比较口语化，意思也是“系上安全带” 。例如：Don't forget to put on your seat belt when driving.（开车时别忘了系上安全带。 ）