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.
The manual holds that women mustn't choose a programme themselves, but instead wait to be assigned to a module. You use a comma before but if it introduces an independent complete clause. As there's no independent clause after but in the sentence presented above, it doesn't need a comma before but. The manual holds that women must not choose a programme themselves, but instead wait to be assigned to a module. Comma usage varies among writers.