Yes, you can use MileagePlus miles to upgrade your seat on United Airlines, and in 2026, the process is well-integrated into the United app and website. You can request a Mileage Upgrade Award from the time of booking until check-in. The number of miles required depends on your original fare class and the cabin you are upgrading to; for some lower-priced economy fares, a cash "co-pay" may be required in addition to the miles. To see your options, log in to your account and go to "My Trips", where you can select the "Upgrade Cabin" option to view real-time availability. If a confirmed upgrade isn't available, you can choose to be placed on a waitlist, and your miles will only be deducted if the upgrade clears. It's important to know that "Basic Economy" tickets are generally ineligible for mileage upgrades. For the best chance of success, look for "PN" or "PZ" fare classes when searching for flights, as these indicate immediate upgrade availability for elite and non-elite members respectively.