I can stop on the way if I'm heading westbound (not too many places though).
Work requires that it be a USA carrier flight number, they don't care who sells or operates it.
If UA operates a flight SIN-DXB or SIN-LHR and the tickets says UA- Great.
If if DL sells me the ticket but it says AF- No Go.
If AA sells me a ticket on QF but it says AA24689 on the ticket- OK.