Fuel stop on way to IAD, the 1 passenger had to get cleared by immigration in main terminal. Next flight, round trip, delayed as all crew had to go to the main terminal and line up at immigration. Next trip, crew change, inbound crew did t go near immigration. So it is "hit and miss".
That sounds ridiculous, surely passengers and crew on private jets shouldn't have to go near the main terminal? Why couldn't immigration just come out to the handling agent's building? I would be pretty peeved if it was me!