Suzeman,
Thanks for the link. Doubtless the CAA will have something too, but the frequency of new
airport design is still close to zero. Within the UK in the last 30 years, we've had - just LCY really? (DSA was a new terminal on a previous military field).
JH,
The advantage of this would be the floor space of the underground terminal building would be much smaller and passengers and crew would have much shorter distances to walk to, from and between gates. Unfortunately that is probably the least likely thing to influence airport designers.
Actually, this will depend on their brief. LCY was very much designed for minimum walking, and I'm sure plenty of contributors here will attest to door open to surface transport times (with luggage) of less than 5 minutes.
Regional airports want to strike the balance right - they play on being more user friendly than the big hubs, but they are making much less per pax than LCY, so they want to boost spending by shoving people into shops.
They also don't 'want' to have people arrive by bus, as they make no money from this. The real easy money is in a surface car park.
However, local authorities may then insist on a Section 106 agreement as part of any expansion plan, which dictates that a certain percentage of passengers must arrive by public transport.