ExpertFlyer is one of the best tools in travel. It’s a paid service that lets you:

• Search for awards and even get emails when space opens up on the flight you want.

• Set alerts for specific seats to open up on your flights, so if you’re not happy in the back of coach or prefer an aisle rather than the window you’ve got you’ll know when one becomes available so you can grab it.

• Find flights with confirmable upgrade space — and get emails when upgrades become available for your flight.

• Get alerted when first class is selling out on your flight, in case you want to use miles or an upgrade coupon to confirm an upgrade instead of waiting for a complimentary one.

There are many other uses for the tool, like checking airfare rules, pulling up seat maps, and seeing the availability of different fare classes on a given flight.

During irregular operations — weather delays, mechanicals — I often was to find out what flights have open seats, and ExpertFlyer is a great way to do that.

Unfortunately in September 2014 Delta made ExpertFlyer remove information about its flights. It often seems that for Delta, an ignorant customer is their best customer.

Last summer ExpertFlyer brought back award availability searches (and emails) for Delta.

And now Delta revenue inventory is back, too.

We’re happy to announce that as of today the previously missing DL data has been restored to ExpertFlyer. The only exception is DL Upgrade class inventory that requires GDS access, which Delta is still not allowing us to use.

However regular fare class inventory/availability/alerting and all the other searches are available again for DL.

And indeed, looking at flights from Detroit to Minneapolis tomorrow I can see how many seats are for sale in each fare bucket on Delta. That’s fantastic.

I’m genuinely thrilled, and of course this makes ExpertFlyer much more valuable for Delta customers.