Parking at airports seems a terrible waste -- expensive parking and your car sits doing nothing. I first started thinking about the various Car Share companies (City CarShare, ZipCar, FlexCar -- effectively membership based hourly car rentals which include gas/insurance and need no human staff) and why one can't use them from the airport. Of course, airports are full of rental car companies, which is a competitive problem, and parking space there is at a premium.
Right now the CarShare services tend to require round-trip rentals, but for airports the right idea would be one-way rentals -- one member drives the car to the airport, and ideally very shortly another member drives the car out of the airport. In an ideal situation, coordinated by cell phone, the 2nd member is waiting at the curb, and you would just hand off the car once it confirms their membership for you. (Members use a code or carry a key fob.) Since you would know in advance before you entered the airport whether somebody is ready, you would know whether to go to short term parking or the curb -- or a planned long-term parking lot with a bit more advance notice so you allocate the extra time for that.
Of course the 2nd member might not want to go to the location you got the car from, which creates the one-way rental problem that carshares seem to need to avoid. Perhaps better balancing algorithms could work, or at worst case, the car might have to wait until somebody from your local depot wants to go there. That's wasteful, though. However, I think this could be made to work as long as the member base is big enough that some member is going in and out of the airport.
I started thinking about something grander though, namely being willing to rent your own private car out to bonded members of a true car sharing service. This is tougher to do but easier to make efficient. The hard part is bonding reliability on the part of all concerned.
Read on for more thinking on it...