score:5
The custom and immigration related regulations for private flights to the US are far too comprehensive to be summarized here. On the CBP web page for private flyers, you can find the most relevant information.
Most regulations are similar for private and non-scheduled commercial flights, e.g. chartered business flights not operating according to a fixed time table.
In all cases, the pilot must file a flight plan and crew + passenger manifest through the APIS system 24 to 48 hours in advance of the flight (depending on the actual flight type). I don't know if the exact verification process of the APIS data is publicly known, but I assume that the US authorities conduct a preliminary immigration check and have the ability to reject passengers even before they departure.
If the flight is from a foreign airport with CBS preclearance facilities, these are obligatory and the flight can commence to any US airport eligible for receiving plecleared flights (the list is available from CBP).
If the flight is from a foreign airport without preclearance facilities, the flight may only commence to US airports with CBP service. If the actual customs and immigration control is conducted separately or together with travelers arriving on regular, commercial flights probably depends on the actual airport facilities.
Upvote:4
When you arrive by corporate jet you have to go through all the same immigration processes that you would if you arrived by scheduled airliner.. The difference is that you won't go through them in a huge immigration hall with banks of agents and lines of people. Typically a single agent will come and do the clearance with all the passengers at once. You still have to fill in the same forms and make the same declarations.