Hi, New to AA & doing 20k BIS in the next 3 weeks for the OW MegaDo EXP challenge. Have a SEA-LHR RT booked next week. Last seg is an AS codeshare. Want to get all miles on AA metal for my challenge, but those were all $250 more. I was hoping to pay the $50 and same day change at the airport onto an equivalent AA flt depending on availability. The other tricky thing is that this is an intl itn which isn't allowed for SDC normally per the AA website. My experience with Delta is that it is generally possible to SDC a domestic leg of an intl ticket when attempted at the airport even on a codeshare as long as you are going to a mainline flt. For Delta it doesn't say this in the rules, but I've done it 5+ times this year. How flexible are AA on their SDC when at the airport? I also have AC access if those agents are better.