A-list and First class

A-list noun - Individuals carefully selected as being the best of a class.

First class and A-list are semantically related. In some cases you can use "First class" instead a noun phrase "A-list".

First class noun - Mail that includes letters and postcards and packages sealed against inspection.

A-list and first class are semantically related. Sometimes you can use "A-list" instead a noun phrase "First class".