定语从句在什么情况下,从句不用紧挨着先行词?

先行词与定语从句隔离
定语从句一般紧跟在先行词之后,但定语从句与先行词之间有时也会插入别的成分,构成先行词与定语从句的隔离.例如：
2) He was the only person in this country who was invited
3)A new master will come tomorrow who will teach you German.明天要来一位新教师教你们德语了.（关系代词who引导的定语从句与其先行词master分离）
其实就是句子顺序倒了一下,你那句子不也可以写作:
Airplane,which usually employed in transporting people,is the most effective means of transportation吗?那就挨着先行词了