There are plenty of ways to earn frequent-flier miles, aside from simply flying on your airline of choice: Sign up for an airline-branded credit card or purchase goods through your airline’s shopping portal, for example. Now, you can add another to the list: Booking hotel stays through websites like Rocketmiles and PointsHound that offer airline frequent-flier miles in exchange for the bookings.

These startups have gained a lot of traction lately, especially since Rocketmiles was acquired by Priceline for about $20 million in March. So does booking your next hotel room through these sites make sense?

It could be a great way to earn a few thousand points that could send you on your way to a free flight, says Daraius Dubash, co-founder of But consumers should know what trade-offs to expect.

Here’s how they work: Log on to the site, enter the city you’re staying in and when, and select which airline’s loyalty program you want to earn points on. (Rocketmiles has relationships with 29 airlines, including biggies like United, JetBlue and British Airways. PointsHound has 22 partners, including JetBlue and American Airlines.) The site turns up a list of hotels available and the number of miles you’d earn for each stay.

The earnings can be quite lucrative: A three-night stay at a London hotel in August earned guests 13,000 miles on United’s loyalty program. They amount of points you can earn varies, but Rocketmiles says you can get up to 5,000 miles per night, while PointsHound advertises up to 6,000 miles per night. The miles are usually credited to your frequent-flier account after you check out of the hotel.

(Hotels pay third-party booking sites a commission for reservations. These sites just take a part of that commission and give it back to the consumer in the form of airline miles, says Dubash.) 

But the rooms you book through those sites may not be at the lowest price available, at least at Rocketmiles. It claims its rates are “in line with other online travel agencies” though “small fluctuations could create price differences.” PointsHound offers a low price guarantee -- if you find a better rate elsewhere, PointsHound will refund the difference.

Still, Dubash says, make sure you check rates before you book. “You don’t want to pay extra just to get the miles. If you’re paying 5 bucks more to get 1,000 miles, that makes sense. If you’re paying 100 bucks more, the math is not in your favor,” he said.

You also forgo earning loyalty points in the hotel’s program itself -- and possibly even some of the perks you might expect as a hotel loyalty program member.

“Oftentimes, you won’t get your elite status benefits, like room upgrades. Some results on the site may give you the option to pay more for that privilege,” said Dubash.

Still, this might be a good option for travelers who don’t stick to one type of hotel and prefer to focus on airline loyalty programs.

Travelers should also check the cancellation policies on each reservation when booking through these websites. While bookings are usually refundable if they are canceled a few days before the stay, each policy is different. And you won’t be calling up the hotel to make said cancellations, or even changes to your reservation. You’ll have to deal directly with Rocketmiles or PointsHound themselves.