I have two strategies for flying J if the employer only pays Y and this is probably the best. But it only works if you can book yourself and get a refund - I explained say 2-3 times I bought a J ticket, showed the Y fare on the same moment, and claimed the Y fare. But if your employer does not give this flexibility, and the rule is they book your ticket (via some contracted travel agent or so), then trying to upgrade yourself is the only way to go. How complex this is will depend on the airline and type of ticket. As indicated you can't cancel the Y ticket and then buy a new one (the refund goes to the original booker, not the one who travels). I was invited to China and my host only could book in Y as per their internal rules. I was lucky that the staff member booking for me could upgrade me simply for the fare difference between the Y-bucket I had and a cheap J bucket when available. They had to pay this at the China side and I paid back (my suspicion is one of my Chinese contacts had to do this via his/her private account - extremely helpful). No issues with cancellation/chance fees of the Y ticket. Thanks to the help I got this worked relatively smooth, but I can imagine with other carriers and other situations it is more complex.