Flights To San Francisco

Hello been reading the answers to questions about flights to Chicago from the UK and the connections and baggage and they were really helpful. I'm flying back from San Francisco to Chicago with United then the United Kingdom with BMI. How does the luggage thing then? Will I have to gather in Chicago, or if it will be booked through? So I must go through customs again to Chicago or what it's done in San Francisco via the UK?

Thank you

You should be able to receive two boarding passes to the SFO, and luggage sent throughout the UK from America and BMI are both members of Star Alliance. In addition, unlike many other countries, you will not have to go through customs or immigration officials when leaving the United States to an international destination, you'll most likely clear the security for a second time Chicago during the transfer of your international flight. Have fun.

if you fly United all the way from your luggage must
automatically be transferred to another carrier
since both airlines are in the same company Alliance
So you will not have to worry about your luggage until
you arrive in the United Kingdom and have to clear customs
if you are traveling from San Francisco to Chicago and
United Kingdom
This is considered a domestic flight there is no customs
involved here
hope this helps