I don't think the US system will check an upgraded pax in unless there is a dm# in the record from which to pull an eupgrade. Can anyone comment on exactly how this works with in Sabre? However, if there is a UA number in the record, the age agent could still operationally upgrade you without using an e-upgrade. Or I believe they also have a way of printing your US e-upgrades. That being said, I'm not sure that (while there may be technical loopholes) that a US GA would be willing to do this. It would probably take a lot of extra computer entries, and the GA might fear if their op upgrades are reviewed. I have no idea to what extent gate agents activities are monitored. The one post on this I remember from a US employee stated that they basically leave agents alone, but that if they are looking to fire or reprimand an agent, they will go back in the system and use his or her waivers as reasons why they might be fired or reprimanded. It is my sense that, conversely, telephone reservations agents are monitored and scrutinized a lot more (like 95% more) than airport agents.