Originally Posted by
percysmith
There should be nothing against a travel agent booking two carriers that will interline to each other on one ticket. You just don't have that much rights on the first carrier (CX) if you book the second on its own code.
But as a general observation - and I'm glad to be corrected - there is no through checking thru the US (some exception for MIA pre-pandemic but not aware for LAX).
Houston is an exception, at least on UA/NH. Though as one still needs to go and clear customers, the benefit of through checking is reduced.