There are travel rewards credit cards that are issued by major credit card issuers, allow earning miles, and are not tied to a particular airline. Such travel rewards credit cards will allow you to earn miles on all your purchases and to redeem earned miles with any airline, including with Norwegian Air. You can keep such cards as your primary card to accumulate more miles. In addition to miles you will be able to earn on your everyday purchases, travel rewards cards often come with a one-time bonus which can be enough for a round-trip reward ticket.
Disclaimer: This editorial content is not provided or commissioned by the credit card issuer(s). Opinions expressed here are the author's alone, not those of the credit card issuer(s), and have not been reviewed, approved or otherwise endorsed by the credit card issuer(s). Reasonable efforts are made to present accurate information, however all information is presented without warranty. Consult a card's issuing bank for the terms & conditions.
All rates and fees, and other terms and conditions of the products mentioned in this article/post are actual as of the last update date but are subject to change. See the current products' Terms & Conditions on the issuing banks' websites.