Premium economy shell seats on Japan Airlines. Premium economy is a travel class offered on some airlines. Positioning in price, comfort, and amenities, this travel class is leveled between economy class and business class. In 1991, EVA Air was the first to introduce Evergreen Class and had since become the first airline to offer this class of service in the world.
This sentence has two independent clauses. They are connected by and with a comma before it. The and and the comma are correct. However, adding a comma after thus is not correct because it is an adverb; the comma after it is not necessary. If thus is used as a conjunctive adverb (without and), a semi-colon and a comma are necessary.
Before as a conjunctionWe use before as a subordinating conjunction. We commonly use before with the past simple tense. It suggests that the second event happened soon after the first one. BeforehandWe can use beforehand as an alternative to before as an adverb, especially when the reference to time is less specific.