Airlines are seriously changing how they play the frequent flyer mile game, which could impact how you travel.

The biggest change is that Delta no longer sells tickets for a fixed amount of miles. Instead, it’s based on supply and demand.

Translation? It can offer whatever it wants, whenever, and with little transparency. More popular routes will most likely require more miles, while less-traveled routes could have a lot more options than before.

There are some other changes, like a new option to upgrade your seat using miles, which you’ll be alerted to when you book.

This isn’t exactly a new strategy: JetBlue, Southwest, and Virgin America already operate their reward programs this way.

But this is a big deal because Delta is the first legacy carrier to follow suit. That means the other major airlines could do the same if it’s successful.

For more information about frequent flyer mileage programs, check out:

• Peter’s Report: How Frequent Flyer Mileage Programs Will Change in 2015
• How You Can Use Your Miles to Buy One-Way Tickets
• Earning Frequent Flyer Miles on Mileage Runs

Keep reading for more travel tips.