United Airlines has announced that it is tweaking its frequent flyer program to reward its most loyal customers better. The new points system rewards customers more for their spending on United’s co-branded credit cards. Under the new program, customers will earn double miles on all purchases made using the airline’s credit card. In addition, they will earn an additional 10% bonus miles on their spending when they use their United Airlines MileagePlus® Explorer Card. Customers can also use their credit cards to earn miles on food and retail purchases. United has also introduced a new tier-based system that rewards customers for reaching certain spending milestones. Customers who spend over $25,000 on the airline’s credit cards within a calendar year will get additional benefits, such as priority boarding and bonus miles.