Expert Flyer is a pay site, though they offer free 5 day trials.
I find it invaluable. Historically it has been a must for any American AAdvantage member since it’s been one of the only sources for real-time availability of American Airlines flight inventory and because it also displays confirmable upgrade availability for American’s flights.
Another key feature of Expert Flyer is the site’s alerts. If the space you want isn’t available, you can tell it to email you when it does become available. It isn’t checking in real-time, but multiple times a day, and with increasing frequency as travel approaches so that I’ve generally found it to approximate real-time pretty well.
When I want an award on a flight I can’t get on, or I want a confirmed upgrade, I set an Expert Flyer alert and I get an email when the space I need opens up (or if I’m debating whether or not to confirm an upgrade, I may set an alert for when space is dwindling).
Just two weeks ago Expert Flyer added support for award space across the Star Alliance.
Now they’ve added British Airways support which I think is great. Many people do try to avoid flying British Airways on award travel because of the fuel surcharges, but it can be useful to know when their flights are available. And BA award inventory mirrors upgrade inventory, which is useful as well.
I’ve got a business class ticket (from the ‘extreme sale’ that BA ran a few months ago) and I’d like to use points to upgrade to first class.
Instead of having to check availability myself every few days, I’ve now set up an email alert.
In addition to British Airways they already supported the following:
Note that their data source for Swiss shows availability offered to Miles & More members, and not to partner airlines. Lufthansa and Singapore availability is partner availability (useful if you’re using miles with United, Aeroplan, Lifemiles, etc — but not as useful if you are using Miles & More or Singapore Airlines Krisflyer miles, respectively).
Also, Expert Flyer only supports some special classes for some airlines (outside Star Alliance). For instance, you can’t do Expert Flyer searches or set alerts for Etihad’s saver award space. They support upgrade searches only.
Here’s the upgrade and award classes Expert Flyer supports for each carrier.