I found this article interesting as I'm always trying to take transit from airports and seeing what's well integrated and what's not. I didn't realize passenger facility charges (PFC's) were blocked from going to transit systems serving the airport. I did find it odd that the author made it seem like so many US airports have train to train systems, when it's not all that many. I guess you could include some shuttle bus to train to be one though. Now it looks like PFC's can go toward transit connections to airports.
U.S. Airports No Longer Have to Build Their Own Terrible Trains
U.S. Airports No Longer Have to Build Their Own Terrible Trains