Originally Posted by
yyznomad
Basic does not allow for upfare. (that's the rule, but I'm sure YMMV if you get an agent who doesn't know or is too lazy to read acpedia)
This'll be the opposite of a normal HUCA situation, looking for someone who doesn't know the rules. I had several flights at the end of 2018 out of several different airports (I was doing segment runs). There were several flights where I'd need to ask the Gate Agent a question prior to boarding. It seemed that each time there was someone wanting to sneak onto the flight I was on as they were at the airport early, etc. Each time the agent took the BP, or looked up the reservation they'd see Basic and politely say that they're on a Basic fare - no changes allowed. There are lots of nuances in fare rules, but I think this basic rule (no pun intended) will be widely known by agents.