They will certainly do this if you miss a connection (because, say, the plane you were supposed to get on never showed up and the one that did eventually arrive

They will certainly do this if you miss a connection (because, say, the plane you were supposed to get on never showed up and the one that did eventually arrive hours later was 50 seats smaller than it was supposed to be and had a malfunctioning main cabin door that had to be repaired before it could take off again... to use a completely hypothetical example). Their system will literally not let them rebook you to somewhere other than your original final destination. I was flying to AMS, but the soonest they could rebook me on a flight there was 24 hours later (late enough to miss the event I was supposed to be attending). They had a perfectly good flight to DUS, which was actually closer to my final destination (by train) than even AMS was, and couldn't put me on that. They finally booked me on a flight to AMS through DUS (with an 18 hour layover), but told me if I got off in DUS, my return ticket would be canceled, thanks to all the people who try to cheat fares this way. On the way, I managed to get one of the agents frustrated enough with her own computer system that she took out a physical pad of paper, stamped it with some kind of official stamp (she had to tick over a counter on the stamp with a special tool), and told me to go show it to the lady around the corner. The lady around the corner worked for a completely different airline, who happily took the piece of paper and gave me a free ticket to DUS. So, yeah, thanks guys, for ruining the system for honest people.