I am flying to Las Vegas in April from Gatwick via Dallas with AA in April. I hold Discount Economy tickets for the trip however would like to upgrade to First Class on the Domestic legss of the trip. I have noticed elite members of the AAdvantage program can upgrade any Economy ticket to First based on availability.

I hold a Silver Excecutive Club Card and was wondering whether I am able to do the same?

Also, do any members have any experience with upgrade priorites on the transatantic legs for Silver members (which I think is sapphire in the one world alliance)?