This is an interesting point. Unlike peer airports that had large scale hubs of similar size (STL and PIT come to mind), CVG is unique in the fact that DL didn't completely abandon their hub operation and maintains a large presence and is even beginning to expand a bit again. Therefore, I fear that they may just do enough to undercut other airlines from significantly expanding, but not enough to build an actual hub to make up for it again. While F9 and G4 have been able to gain a foothold in CVG, DL may view WN as more of a legitimate thread and may do much more to undercut them.
I think this is a legitimate concern. CVG is reinventing itself but this is in large part due to new carriers with new fare structures that the O&D traveler has embraced. This wouldn’t have happened had Delta not created a tremendous void through its downsizing. New carriers trying to get a foothold in CVG back in DL’s heyday were matched on price and quickly driven out of the market when the public ran back to DL. To avoid history repeating itself, people should support the new carriers and not run back to Delta when it tries to restablish routes it cut. Diversity of airlines will drive CVG’s future, not a return to hub for DL or anyone else. I’m a fan of DL and I like that they focus on CVG. But I don’t want to return to the days where they become competitive only long enough to drive the competition off and then raise fares to unconscionable levels because they are the only game in town.
WN successfully competes against DL on DAL-ATL, DAL-DTW, DAL-LAX, DAL-LGA, and DAL-SLC nonstop service. The situation has also changed in the DFW Metroplex with Delta eliminating its DFW hub 13 years ago, with the repeal of the Wright Amendment, and with WN adding nonstop service from DAL to Delta's ATL, DTW, LAX, LGA, SLC, and SEA hubs plus Delta's BOS and RDU focus cities.
WN would also be able to connect passengers from CVG to at least ABQ, AMA, AUS, ELP, HOU, LIT, LBB, MAF, OKC, SAT, and TUL through DAL if it adds DAL-CVG nonstop service. DL, on the other hand, is more reliant on nonstop travel between DFW and CVG on its DFW-CVG nonstop flights, and DL cannot connect passengers to these destinations from CVG through DFW on its DFW-CVG nonstop flights.
DL does not serve AMA, CRP, LBB, and MAF, but WN would be able to connect passengers to these smaller Texas markets from CVG through DAL and HOU if it adds CVG-DAL and CVG-HOU nonstop service.
WN can do well on DAL-CVG nonstop service if it adds DAL-CVG nonstop service since there is probably enough demand for DAL-CVG nonstop service with F9 doing DFW-CVG nonstop service on a seasonal, less-than-daily basis, since WN has been able to successfully compete against DL on nonstop routes to other DL hubs from DAL, and since there are many travelers in Texas who would still choose to fly on WN to CVG if DL did lower DFW-CVG fares in response to WN adding DAL-CVG nonstop service.
DAL is located in the City of Dallas and is much closer to Downtown Dallas than DFW Airport is, and the convenience factor would probably cause some Cincinnati-area travelers to choose to fly to DAL on WN over DFW on DL if WN adds DAL-CVG nonstop service. On the other hand, there are some Cincinnati-area customers who are loyal to DL and who would choose to fly on DL to DFW, even if WN adds DAL-CVG nonstop service.