Shopping portal rewards and a short-term bonus let you earn a bunch of United miles when buying airline tickets — even if the tickets you’re buying are for flights on Delta and American Airlines.

United’s MileagePlus mall is offering half a mile per dollar spent at Expedia.

There are a handful of restrictions but not many. You earn United miles on airline ticket purchases and even car rentals. (You’d earn miles on hotels, too, but I’d rarely ever want to book hotels through Expedia — there are far more lucrative places to go for that and you lose out on loyalty points and elite status credit too.)

Not eligible on any rental car transaction exceeding a purchase price of $5,000 USD. Itinerary changes may void eligibility. Not eligible on Port Charges for Cruises or on Travel Insurance. Not eligible on event tickets. Not eligible on 3PP vacation packages or cruises sold through Expedia.ca. Not eligible on purchase of Expedia.ca pre-packaged vacations. Not eligible on Groupon Getaways purchases. Not eligible on taxes and fees. Not eligible on purchases made with coupon or discount codes that are not found on this site.

This offer stacks with the current bonus of up to 1700 United miles for shopping portal purchases.

Cumulative purchases through May 19 of $150 earns 500 bonus miles or $300 spend earns 1000 miles. $300 in ticket purchases, therefore, earns 1150 United MileagePlus miles — whether those are United tickets or other airline tickets. You can buy Delta tickets through the MileagePlus shopping portal and earn United miles for doing so.

Historically airline shopping portal sites have excluded rewards for online travel agency bookings, since a bonus like this makes it attractive to book United tickets at Expedia instead of United.com. And it’s especially strange to see this right now when United is in the midst of a major battle with Expedia over the terms on which Expedia will offer United’s flights going forward. However the shopping portal is a third party business, buying United miles, and the right people probably aren’t talking to each other here.

The United MileagePlus mall isn’t the only place to earn miles for purchases through Expedia. You can earn a flat 136 Virgin Atlantic miles. You can earn a flat 135 Spirit Airlines miles. Ebates gives you $1.25 on flights and 1.5% on car rentals. Wells Fargo and Barclays offer rewards for Expedia purchases, too.

For some of you the rewards won’t make booking through Expedia worthwhile. When things go wrong or you need to make changes dealing with Expedia can be a pain.

It always amazes me that the online travel agency sites aren’t better. Their business is connecting people with the travel experiences they’re looking for. They should do a better job understanding what a customer wants and matching that to the best itinerary or hotel choice possible, and making it really easy to get exactly what the customer is after. And yet in my experience customer service when booking through these sites is really bad.

(HT: One Mile at a Time)