Tim Winship sketches the plan for Delta’s new three-tiered award structure.

Regular readers of this blog know that on December 1, Delta axed the ability of its Skymiles members to use additional miles for last-seat availability.

But the option will be coming back, albeit with a higher mileage price than before.

Robertson also elaborated on plans for a revamped award structure, to be rolled out sometime this summer.

The SkySaver awards will remain as is, allowing SkyMiles members to redeem 25,000 miles for a capacity-controlled domestic coach ticket. But the less restricted SkyChoice awards will be split into two tiers.

Using the current SkyChoice domestic award as an example, Robertson explained that in place of the current 50,000-mile award, there would be a 60,000-mile award which guarantees last-seat availability, and a 40,000-mile award which would stop short of last-seat access but offer better availability than the SkySaver award.

If these are the award levels that are introduced come summer, then the change isn’t nearly as bad as it sounds at first blush, since Delta allows you to mix and match different classes of service and different price levels on a single award.

So you should be able to redeem one-way for half a 25,000 mile award (12,500 miles) if that’s available, and half a 60,000 mile last-seat availability award (30,000 miles) for a total of 42,500 miles roundtrip. That’s better than 50,000 miles, the only choice if the 25,000 mile award wasn’t available in both directions prior to introducing combinable awards in December 2006. And it’s not much more than the 37,500 miles it would have taken to combine a capacity controlled and last seat availability award before the recent changes.

Meanwhile, a likely scenario is finding mid-priced award availability in one direction and last-seat availability in the other. The cost in miles? 50,000. The same as the old last-seat availability award. The only time you’ll spend more than 50,000 miles is when you’re booking extremely sold out flights in both directions.

Before you get too excited, though, it’s worth remembering that United still offers last seat availability at 45,000 miles. And up until a year and a half ago, United made it available at just 40,000 miles. Delta is becoming less competitive in its award pricing, a trend that they’ve been on for some time.

The worry, of course, is that other airlines follow Delta’s lead here.