Expert Flyer is one of my favorite tools.

• I use it when I need to find flights with available seats, such as during weather events or when my own flight goes mechanical.

• It helps find award seats on a variety of (though far from all) airlines.

• They can email you when seats open up. They have ‘alerts’ you can set so when inventory because available that you’re looking for (for an airline and class of service they support) you get an email.

• They’re the only service I know that displays American Airlines upgrade inventory (A for first class upgrades, C for business class upgrades). When I really care about a domestic upgrade I set an alert for cofnirmed upgrade space disappearing (e.g. “fewer than 3 “A” seats left) and then I know if I want to be sure of clearing I need to confirm it.

• Their ‘seat alerts’ are useful on heavily booked flights — If I need to take a flight where there aren’t extra legroom seats, or aisle seats, or I want an exit row that’s not available — I set an alert and get an email when one of those seats opens up (this usually happens close to departure, someone clears an upgrade and a seat I want frees up).

They have many other features as well.

One of the disappointing things, though, is that about 10 months ago Delta forced Expert Flyer to remove everything about the airline from its site.

And while Expert Flyer doesn’t show Delta’s revenue fare buckets, or upgrades, anymore they’ve just introduced Delta award searches and that means you can get email alerts for space opening up.

Two key things to know:

• They only show whether the awards you’re searching are available or not, they don’t show the number of award seats that are available on a given flight.

• They only show lowest (saver) award space, they don’t show the higher tier award buckets.

And since it searches for space, you can set up a flight alert. There were no first class award seats on Delta 2753 San Francisco – Los Angeles on September 15. Here I’m setting up a search for 2 first class saver awards (“R” seats) on that flight. Expert Flyer will email me if and when those seats open up.

Expert Flyer currently supports awards for 56 airlines. That means you can get availability alerts when awards open up on any of those carriers. Note, though, that in a couple of cases (like Swiss) it’s availability as seen by members of the airline’s own program. And so if you’re using United miles you may not be able to get those seats.

I find it especially useful for American, Emirates, Etihad, and Iberia to name just a few.

Here’s Expert Flyer’s FAQ About Delta Award Searches:

Are all DL award tiers being shown?

No, just the lowest level award classes R (First), O (Business), N (Economy).

What flights will be shown for the DL award search?

DL operated flights only.

Can we set Flight Alerts and be alerted for inventory for those classes?

Yes! Flight Alerts can be set either from the Award & Upgrade results for shown DL flights, or via the Create New Flight Alert page.

Does this mean that upgrade availability is being shown again?

No, the R and O classes being shown represent awards, not upgrades. Upgrade inventory was only available via the reservation systems (GDS) which Delta is preventing us from using for accessing their data.

Does this mean that the other non-award DL data (fare classes, seat maps, etc) will be returning to ExpertFlyer?

No, Delta still is preventing us from accessing any reservation system (GDS) data.

So why are you doing it?

We think it is in the best interest of our customers.