High long time lurker and first time poster. I really enjoy reading the wealth of information that is in this board. But to my question.

With the summer upgrade promo I thought that the only conditions on upgrades were it must be tango plus and within North America. So i went and booked a flight.

I Booked a flight for july 26 into tango plus, booking class s.
july 26ac224-yvr-yyc
july 27 ac1178-yyz-yyz
july 27 ac916 - yyz-mia

august 14
ac917 -mia-yyz
ac017- yyz-yver

I checked the level of people in first and these flights seemed the emptiest. However after booking, I realized I should have plugged in the "only show upgradable fares" box. When I went back to look at the arrow that points up, next to upgradable fares, it was not only any of the flights I had booked. Now is this because these flights can not be upgraded or have people already filled all R inventory. Now what would be the best way of going about booking a flight from yvr-mia with the highest probability of being upgraded. I have 24 hours to change my flight free of charge(I believe). Thanks for any help in advance. This forum has really helped me in my first year as an E and possibly SE.