Well - that's what people thought with Frontier/SWA. You'll get some senior pilots who say, "if I wanted to go to Delta, I would of gone - I want DOH or 1:1 for a merger, etc if you want it to happen."

Personally, I can't see why Delta would be interested in Spirit. True, Spirit has a lot of Latin America routes, but it's all ultra-low cost flying. If Delta bought Spirit, and put a Delta cost structure onto those route, I can't see much profit to be had.

Delta goes to 30 of the 33 destinations that Spirit goes to, so it wouldn't be much in the way of additions to the route map.

The only thing I could see Delta wanting from Spirit are the airplanes. But, Spirit management seems to see the benefit of selling airplanes for a profit, so I don't think the airline would be cheap. (ie, by buying Spirit I don't think Delta would get the airplane for a song.) If I recall, Spirit sold some of the their Airbuses to Tiger Airlines in Asia - presumably for a profit.

Someone correct me if I'm wrong, but I don't think many of Spirit's routes are exclusive - ie, the are routes that only Spirit can fly. I think if Delta wanted to fly most of the routes, they could just start flying them.