I have encountered the following two sentences in Rosetta Stone Spanish course:
Los pasajeros de la clase turista comen.
Los pasajeros de primera clase comen.
It seems that if you mention economy class, you express it as la clase turista, but on first class, you express it as primera clase.
Why does the latter case not use an article?
Why does the latter case use an adjective before the class?
How can I distinguish the other cases such as business class or premium economy?
NOTE: Please answer the question in English.