This should be a simple query on the web, but I'm not locating the right database.

I'm looking for the amount of passenger traffic CONNECTING through
airports in the U.S. What's known as D&O (dest and orig) is excluded-
specifically I want how many people pass through airports only in
transit or connecting to another flight. I need the source citation.

I don't think I can pay a bonus but it'd be really helpful to know the
layover distribution (100,000 passangers at 2 hrs, 200,000 passangers
at 1 hrs, etc.) too.

I've checked the ACI-NA numbers, the FAA, and the BTS websites, but
have not directly found this data. The only indirect reference I found
was an airline hub price analysis from 2000, which shows % of
passengers changing planes, but it is too stale.

Thanks.