Some airports in the US are trialling the transit thru check for pax just doing TWOV. AFAIK ATL, DFW & MIA are part of it, so if you are using the pilot FIS in a gateway and are continuing on the right airline, you may get lucky! MIA used to have a holding pen for transit without US immigration, but that got nixed recently. Some FTers tried it for kicks and reported sitting in a windowless room among deportees to s./c.america