That's what we do the modeling of the travel demand factors to estimate ridership changes. No idea connecting to the Airport should be dismissed. Major airports are special generators, with high employment levels, not just passengers needing access, and often have high parking costs. All factors that influence transit use, if available. So we see a fair amount of passengers, but often many more work trips, at airports with transit access like Atlanta.

I suspect this is also true for BART and SFO (if anyone has a data base on who uses BART to SFO or link that would be interesting to see). I expect an increase when the Crenshaw LRT opens next year, which will really improve connectivity to LAX employment, and with the new people mover for access from the LRT to the terminals.

On the other hand, I've also seen the case where airport parking franchisee's, private parking lot operators, airport shuttle operators are huge campaign contributors, and have blocked access at some airports. I was around, back when the dinosaurs still roamed, at the dawn of LA rail transit planning, when a certain councilmember kept blocking the Green Line, stalling any decision for a couple of years, until they were finally voted out of office.

It sound to me like VTA has to make some tough decisions, because in the past, they've made some decisions that were not well thought out. They are running empty trains on segments because of poor planning, poor resultant ridership, and an operating budget shortfall that must be covered. A capital project like you suggest takes years and millions, if not hundreds of millions... So it's not going to fix the short term problem they face.