Originally Posted by
dimramon
I still am not sure how it could be back to back ticketing, since ticket A is DEN-AMS; BRU-DEN and ticket B DEN-AMS-DEN.
That doesn't matter. It's a myth that only A-B-A and B-A-B constitute back-to-back ticketing. UA spells out the definition, and they've been posted above multiple times.