Originally Posted by
Often1
Separate itineraries doesn't matter. It's whether it's one or two tickets. If separate tickets, the theoretical policy is no.
There is no such "policy." Currently, UA will absolutely interline bags, particularly where you are interlining to a *A carrier. In fact, the
official policy as of 3/1/15 will be that UA will
only interline to a *A carrier across separate tickets.
United Eliminating Checked Bags on Separate Tickets Outside Star Alliance