Originally Posted by
weibelt
Would it work to just scan the LAX-DEN-YYY and not the XXX-LAX-DEN boarding pass, knowing that I would only then have 1 seat, or might they preemptively cancel the LAX-DEN-YYY ticket?
If they notice it, they will preemptively cancel one of the reservations (likely LAX-DEN-YYY, because that's the one that's ticketed with them).
They might not notice, however, in which case you would get to YYY at the price you want, but without the empty seat.
If your other reservation is an award ticket, and your UA frequent flyer number is on (at most) one of the reservations, they might not notice, especially if your name is fairly common. Nobody would be surprised if there were two John Smiths on an LAX-DEN flight.