I honestly think we should approach regional rail and airline travel as a codeshare. United codeshares flights around the world I can buy a ticket to Moscow from United and it's on Lufthansa from Germany on but it's still a United Ticket. Honestly what I think would make a lot of sense is to eliminate some of these short inefficient EAS Flights that make no sense and pass it over to rail.
My best example is the Charlotte airport which has a rail yard between two of the runways. Put a station there and you can run service to Greenville, Greensboro, Raleigh, Columbia, Charleston, and Asheville which all are close to the shortest flights in the American Airlines system. These could be better serviced by rail than a flight because no one is flying from Columbia to Charlotte, it is 99.9 percent connecting traffic.
The train would work better in the instance of Columbia-Charlotte because it can pick up people closer to their homes. For me it's an hour to drive to CAE, or an hour and a half to CLT. But if I can start my journey on a codeshared train to Charlotte airport that's a winner. With it being a codeshare if the train is late AA would have to accommodate me. It would eliminate expensive airport parking as well. Improve congestion at the airport as the train can make extra stops such as Rock Hill and Fort Mill that drive to the Charlotte airport. And American benefits from not having to contract with regional airlines to fly the route.
Which is good for the environment and the bottom line because less employees to pay at the end of the day. It would also free up some slots for AA that they could then use on higher profit routes out of their hubs. Essentially this would work the same out of almost all of the major airports IAD/DCA/BWI, ORD/MDW, ATL, DEN, SFO, LAX/BUR/ONT, BOS, JFK/LGA/EWR
I have always wondered if you could fund the short corridor trains from a private company as I could see Delta in Atlanta wanting to do something like this. Delta has a lot of flights all over the southeast that could easily be replaced fully or partly by rail such as Birmingham, Montgomery, Chattanooga, Greenville, Augusta, Savannah, Valdosta, Jacksonville, etc...
It would be cheaper for Delta and they could get back some of the slots in Atlanta to run high profit transcons, or intercons.