How To Spend United Airlines MileagePlus Miles

United MileagePlus is United Airlines' miles and loyalty program; once miles have been earned, there are many ways to spend them. Using miles for flights is the most obvious (and best value) choice. With the shift to less transparent pricing, partner flights tend to offer better value now. There are other uses as well, including some good value upgrading options. This guide takes a look at the main ways to spend miles and where the best value lies.