First class and Intercontinental

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

Intercontinental and first class are semantically related. In some cases you can use "Intercontinental" instead an adjective phrase "First class".

Intercontinental adjective - Extending or taking place between or among continents.

First class and intercontinental are semantically related. Sometimes you can use "First class" instead an adjective "Intercontinental".