Heads up, United flyers! If you're running low on MileagePlus miles and have a trip in mind, United is offering a promotion where you can buy miles with up to a 100% bonus. This means you could snag miles for as little as 1.88 cents each. The sale runs until January 26, 2026, giving you plenty of time to decide if it's right for you. Now, before you jump in, there's always a "but" – and this is it. While a 100% bonus sounds amazing, these mileage sales are rarely the slam-dunk deals they appear to be at first glance. It only makes sense to buy miles if you have a specific, high-value redemption in mind, like a business class flight that would otherwise cost way more in cash. Otherwise, you're better off earning miles through flying or credit card spending. Do the math carefully before you buy!