If Memphis was Northwest’s way of getting geographically beyond its core hubs, Cincinnati did the same thing for Delta but in reverse. Delta was already strong in the south with the impenetrable Atlanta hub, but Cincinnati gave the airline a place further north. After the Northwest merger gave Delta the Minneapolis/St Paul and Detroit hubs, Delta’s second-largest hub in Cincinnati was doomed. It had farther to fall than most.
For some reason, I find Cincinnati’s entire terminal plan to be just about the most confusing thing around. I believe the original Terminal A was knocked down at some point, but best I can tell, by the time the 1980s came around, there were three separate terminals called B, C, and D.

Delta built up its hub there largely on the back of regional carrier Comair which became a key partner. Comair was also the first operator of the CRJ regional jet, and it needed a terminal to support its growth. Terminals B and C were renamed Terminals 1 and 2. Those were for all the other airlines. Then Terminal D was demolished and a new Terminal 3 was built for Delta and Comair on top of it.

Terminal 3 was huge. It was connected by underground walkway to new concourses A and B. Then a new concourse C was built to the west that required a shuttle that was the home of the regional jets. In 2005, the airport had over 600 daily departures and more than 16 million departing seats. Almost all of those were flying for Delta. But then Delta filed for bankruptcy, and the hub began to fall apart.
In 2006, there were fewer than 450 daily departures, and Terminal 1 was closed. By 2008, traffic had dropped enough that Concourse C was shuttered. And in 2010, Delta closed Concourse A and moved it entire operation into Concourse B alone. In 2012, the airport made the wise move to close Terminal 2 and move all those airlines into the abandoned Concourse A in Terminal 3. By the time 2014 rolled around, the airport had just over 130 daily departures with a mere 3.5 million departing seats. That is absolutely heartbreaking for any airport to endure.
With too much closed infrastructure sitting around, it was time to clean things up.

In 2016, Concourse C was razed, and you wouldn’t know it ever existed. The same fate was in store for Terminals 1 and 2 in 2017. The only remaining terminal and its two remaining concourses were renovated, and a new rental car center was buillt on top of where the old terminals used to exist.
The last few years post-pandemic have seen Cincinnati fall into a roughly 125 daily flight pattern with over 5 million annual departing seats. It is a shell of its former existence, but it’s one that now entirely serves the local market. No airport has fallen harder than this one, and I can’t imagine it has been an easy road for anyone in the region.
