Originally Posted by Gardyloo

I'd probably do a Platinum challenge on AA; IMO Delta's redemption picture is miserable. Unfortunately AA/US only serves YOW via CLT or PHL, making for long detours en route to the west coast. However, AA allows credit to Westjet; so routes like YOW-xYYC-SEA would be mileage-earning, using AS for the YYC-SEA segment.

You won't get lounge access with status on AA; nothing on US/Mexico/Canada/Caribbean routes with a very few exceptions.

I wonder if you ought to look at Alaska Airlines instead? You can earn AS miles on AA or DL flights, and their partners list and redemption rates are excellent.

Then just buy an Admiral's Club or Piority Pass membership for the lounge bit and call it good.