Feb 19 (Reuters) - United Airlines UAL.O is revamping its frequent-flyer loyalty program to further reward travelers who carry a United co‑branded credit or debit card, while dialing back mileage earning for members who do not.

The airline said the changes are designed to boost adoption and usage of its card products.

Across the industry, loyalty programs have evolved into major profit engines, with carriers earning billions of dollars each year by selling frequent-flyer miles to banking partners tied to those credit card portfolios.

United Airlines' primary MileagePlus cardholders will be able to earn up to twice as many miles per dollar spent on United flights compared with non-cardholders, the carrier said. This will come into effect with tickets purchased on or after April 2.

The cardholders will also receive at least a 10% discount when booking tickets using points or miles.

"MileagePlus is designed to reward loyalty to United, and our best customers deserve the best benefits in the industry," said Andrew Nocella, United's chief commercial officer.

The overhaul tightens rules for non-cardholders.

United said MileagePlus members without a co-branded card will earn fewer miles on flights, while general members will not earn miles on basic economy tickets unless they hold a card.

(Reporting by Shivansh Tiwary in Bengaluru; Editing by Krishna Chandra Eluri)

((Shivansh.Tiwary@thomsonreuters.com; +91 9708363192; X: @Shivansh_19_;))