Update: Some offers mentioned below are no longer available. View the current offers here.As we’ve written about before, airline shopping portals are a great way to boost your earnings on everyday purchases with a variety of online retailers. These sites sometimes offer promotions with increased earning rates or one-time bonuses for hitting a purchase threshold, and today, United Airlines frequent flyers are in luck. United MileagePlus Shopping has just announced its fall promotion, the Bon Voyage Sweepstakes, which is offering a grand prize payout of 100,000 award miles and $2,500 in cash to one lucky winner.The Bon Voyage Sweepstakes promotion actually consists of three components:A sweepstakesIncreased earning rates at select merchantsBonus miles for new members of MileagePlus ShoppingThe promotion starts today (September 12) and runs through 11:59pm ET on September 29, 2017, giving you just over two weeks to take advantage of it. Let’s take a closer look at each offer to see how you can walk away with a nice haul of United miles.The sweepstakes grand prize will get you four domestic round-trip award tickets on United.SweepstakesThe first part of the promotion is a sweepstakes offer with a grand prize of 100,000 United miles, plus $2,500 in cash to offset the taxes that you’d need pay if you win — check out TPG’s post on minimizing prize tax burdens if you do happen to come out a winner. There are also three first prizes of 20,000 miles each. You can earn entries in three different ways:Registering for the sweepstakes earns 1 entry.Opting into marketing emails from MileagePlus Shopping earns 100 entries.Making a qualified purchase of $50 through the portal earns 20 entries (you can earn up to 100 per day this way).We often write about contests being offered by various travel providers, and like always, the odds of winning any of these prizes depends on the number of entries received. Still, it never hurts to try; you can’t win without entering! If you wanted to earn the maximum number of entries, you’d need to complete the first two items and then complete five purchases per day throughout the promotion. This would give you a total of 1,901 entries; that’s nowhere near a guarantee of winning, but you’d certainly have better odds than most!Sign up for our daily newsletterEmail addressSign upI would like to subscribe to The Points Guy newsletters and special email promotions. The Points Guy will not share or sell your email. See privacy policy.Increased Earning RatesAnother part of the promotion is an increased earning rate at select merchants. Generally speaking, most of these shopping portals offer just 1-2 miles per dollar spent at the most popular merchants. However, through the Bon Voyage Sweepstakes promotion, you can earn almost 5 times more miles when you make purchases at select merchants. Just be aware that these increases are not in effect for the entire promotional period, and most increased earning rates will return to normal after 3-5 days, so be sure to act fast. Here’s a glimpse of some of the offers:MerchantOld Earning RateNew Earning RateGroupon3 miles/dollar10 miles/dollarHP2 miles/dollar4 miles/dollarNeiman Marcus2 miles/dollar4 miles/dollarBest Buy 0.5 miles/dollar 2 miles/dollarNew Member OfferMileagePlus Shopping is offering an additional amount of bonus miles for new members of the program. If you have the United MileagePlus Explorer Card, you’ll earn 1,000 bonus award miles after you spend $150 within two weeks of joining MileagePlus Shopping. If you’re not a cardholder, you can still earn a bonus, too. You can earn 500 bonus miles if you spend $125 within two weeks of joining.Bottom LineWith the opportunity to submit so many entries, it’s definitely worth entering United’s Bon Voyage Sweepstakes. Plus, the ability to earn miles at an elevated rate with select retailers make this promotion even more attractive, especially when you spend on a card like the United MileagePlus Explorer Card that will allow you to boost your earnings even further.Will you be taking advantage of this new promotion?