Extra baggage on a multi-segment flight
 

Hello,
I am going to have the following journey:
LIN-FCO-LAX-SBA

LIN-FCO-LAX is with one carriere (Alitalia, AZ), LAX-SBA with another (United Airlines, UA). I bought the two tickets separately.

I have an extra baggage, so I have to pay for it at LIN airport. Do I have to pay for it at LAX airport too? Can I ask to tag the baggage for SBA when I check-in it at LIN airport? Are there precise rules for this kind of situations?

I know that at LAX, international passenger must, in any case, take its baggage for custom checks, but I think that there is a way to transfer it to another flight without checking-in it (and without paying for it) again.

Thank you.

Extra baggage on a multi-segment flight
 

Yes. You have to pay for it at LAX too.

ua & az should have an interline agreement for bags.....

show the 2 tickets at check in & ask for the bags to be checked thru.....should work...