ExpertFlyer is a paid subscription service that I find incredibly useful for searching award space, looking at flight loads, and setting availability alerts. It looks like it got a bit less useful for Delta flyers as of yesterday, unfortunately.
Per an email sent out to ExpertFlyer members:
Dear ExpertFlyer Subscriber,
As of today, Delta has requested that we remove the visibility of the DL elite upgrade classes (RU/OU) from ExpertFlyer.com. As such, your Flight Alerts for these 2 classes can no longer check for availability in those classes so their status has been changed to Expired so they do not count against your available alert allocation.
If you would like to send feedback to Delta regarding their decision and how it may affect you, please use the following link to email them. Delta Email Feedback
As always, thank you for your support of ExpertFlyer.
-The ExpertFlyer.com Team
Definitely a sad development, though it’s also a trend I’m noticing lately whereby airlines want more control not only over what information is distributed, but how it’s distributed. We’ve seen this with AwardWallet as well, whereby airlines prevent them from displaying mileage balances, as they’d rather drive people to their own websites.
The good news in this case is that it’s actually still possible to search upgrade space on delta.com if you’re an elite member. Simply make a “dummy” booking for the route you want to search upgrade space on, and on the search page space specify you want to book a full “Y” ticket.

Then on the results page you’ll see a button that reads “Upgrade Eligibility.” If the flight has confirmable upgrade space it’ll display “Upgrade Available,” while if it’s not confirmable it’ll display “Upgrade Eligible.”

I’d definitely recommend sharing some “feedback” with Delta if you found the upgrade space being displayed on ExpertFlyer to be useful…
Membership is free and takes no more information than commenting as a guest. Earn status points for good contributions, and see fewer ads as your status grows.