Virgin Atlantic Flying Club members can opt to pay more when booking flights to get a “Miles Booster”–earning double or triple the miles you would normally earn for the flight. And every time you pay for a Miles Booster, you’ll get an additional 1,000 bonus miles. You can purchase miles through Miles Booster from the time of booking the flight until the original date of the first sector of the flight itinerary or up to the date six months following the original date of the first sector of the flight itinerary.

The cost of the miles varies depending on the number of miles included in each purchase. As an example, a roundtrip flight between London Heathrow and Miami would typically earn 8,860 miles. With Miles Booster, you can get 18,270 miles (double base miles plus 1,000 bonus miles) for a cost of #178 or $247.

To use Miles Booster, you can book on 0844 874 7747 in the U.K. or (800) 821-5438 in the U.S.

Bottom line: At $247 for 9,860 miles, the cost per mile is $0.025. Virgin Atlantic is not the only airline to feature an easy way to buy miles when purchasing flights, and although it’s convenient, but be sure to do the math to determine if the cost is worth the extra miles you’ll get.