It’s becoming increasingly common for airlines to offer extra miles in conjunction with a flight–for a fee, of course. United Airlines started the trend with its Award Accelerator, followed by Alaska Airlines and now Hawaiian Airlines has joined the airlines who are offering members the option to purchase additional miles at a lower cost than buying miles without flying.

HawaiianMiles members on qualifying interisland, transpacific and South Pacific Hawaiian Airlines flights can choose to double or triple their miles when flying on qualifying itineraries. This option to purchase miles in conjunction with a ticket purchase gives the member a discounted rate on the miles as opposed to purchasing miles straight from the airline to top off for an award. For example, doubling your miles on an interisland flight (an extra 500 miles) would cost $9.10 plus 7.5 percent federal tax and tripling your miles (an extra 1,000 miles) would cost $17.60 plus 7.5 percent federal tax.

When purchasing a ticket online at HawaiianAirlines.com, members will receive the MilesMaximizer offer on the confirmation page as well as the confirmation email. MilesMaximizer double or triple flight miles will post to the member’s account upon purchase.

Bottom line: Purchasing miles directly from the airline costs $.025 per mile plus 7.5 percent tax, or $12.50 per 500 miles. A member would save $7.40 when using the MilesMaximizer to acquire 1,000 miles instead of buying miles without a flight. Buying miles is always more expensive then earning them for free and you won’t save a lot with MilesMaximizer, but the difference could be substantial on large mileage purchases.