United Airlines Mile Play stealth promotions
Every few months, United Airlines will roll out these "stealth promotions." These are targeted offers that allow travelers to earn extra miles for completing a certain number of requirements. The promotions are targeted and will generally fit your travel patterns. For instance, members who haven’t flown United much recently tend to be targeted for more compelling offers. You won't get rich from Mile Play but it can help you get to that next award faster without any cost to you.
These offers will sometimes pop up on the home page of the United app or in your email. However, more often than not you're going to need to check online periodically to see if you're targeted. United has a webpage dedicated to Mile Play. All you need to do is enter your Mileage Plus number to see if you're eligible and register.
It's important to dig into the terms and conditions of any offer. As a general rule, award flights are not eligible for Mile Play promotions. Also, there will frequently be a minimum spending requirement for these promotions, whether overall or per flight.
In the past, TPG staff members have received a variety of offers, including earning 2,500 to 8,000 bonus miles just for booking one round-trip ticket on United Airlines. While I don't have any current Mile Play offers, I have been targeted three times over the past year:

Clearly, I need to be better at practicing what I preach. While I wasn't traveling very often in April of this past year, I was back to a pretty heavy business travel schedule in September. I never bothered to check Mile Play and missed out on an easy 5,000 miles. According to TPG's current valuations, that's roughly $57 worth of miles that I left on the table. Hopefully, that's a mistake I won't make again.
Related: What is United Airlines elite status worth?
Bottom line
There are very few "free" miles out there. Generally speaking, you're going to give up earning miles or points somewhere else or forego earning lucrative cash back on purchases. Mile Play is a unique opportunity for loyal or even occasional United fliers to earn extra miles for flights you were planning to book anyway. Set a reminder in your calendar to check once a month to see if you're targeted for an opportunity to get closer to your next award flight.









