Turkish Air is easy. Just apply for the basic card and send in a photo of your current card and a pdf of your last years account. it takes about 3 days to a week. See the TK forums for better details. this is valid for 2 years! amazing

jasper is correct though AC has a better upgrade program. Welll you get better oppertunity to upgrade with e upgrade credits. I unfortunatly ended up with the same amount of credits I started the year with. It all depends on your flying habits and if you take the road less traveled(with open spots.) i am unlucky that way. with tk you can buy an upgrade with miles.

The other thing to consider, which i did, is that you now can only upgrade tango plus rather than tango. This is a considerablably more expensive fare in my experience