Really enjoyed a recent European rail trip but quickly discovered mixing flight and rail is problematic if the links between airport and train station suck
The French tried: both Paris CDG and Lyon airports have TGV stations in them. There was a time the trains were even code-shared and you could book them as regular connections.
It was very convenient when it worked, for example from the US to other cities or ski resorts in France. But that was 10 years ago, and I haven't looked into it recently, so I'm not sure if they developed it or not.
