I used to be a gate agent for US in TYS. I can remember on more than one occasion passengers coming up the jetbridge and asking me what city they were in. One time a passenger was flying something like BOS-DCA-GSO, but in DC, she boarded DCA-TYS. So, when she got to TYS, I had to reroute her TYS-CLT-GSO. If she were FT savy, she might have done it on purpose to get the extra segments. ;-D

It was most common from DCA with the whole 35A one gate for every flight boarding mess, but it happened from other cities too.

In TYS, we had three departures back to back in the afternoon, and we would use one gate for two of them. I remember many times a passenger would try to board the wrong flight and if you weren't really paying attention, you'd sometimes let a few slip buy. When our counts didn't match up, we'd figure it out. Of course, we didn't have boarding pass scanners. We did manual seat entry so if you waited to input the seats, you wouldn't catch the dupe seat or a seat assignment not actually assigned on the flight until you put it in.

If I qualified by segments for PM, I'd try a little more of this!