My mockup isn't perfect, and it wasn't intended to be. Your questions and requirements are all valid. Considering the current site acceptable is what bothers me.
I don't know the answer to that, but AA is run by business people so I would wager that the answer is "no," otherwise they would be doing it already.
I think there are some intangible benefits to having a more usable website, but those are intrinsically difficult/impossible to measure so they don't factor into the business decisions.
As a designer, I feel your pain, but the unfortunate reality of the situation is that AA is driven by their bottom line and a more usable website probably won't net them the greatest ROI right now.
I would rather have "business people" running GM than someone who thinks that redesigning the GM website will solve all their woes...or any of their woes.
What percentage of AA's bookings come from their website, and what percentages come from travel sites like expedia or from travel agents. I know a large number of AA's customers are business travelers.
If 10% of bookings come from the website and they are able to increase it's effectiveness 50%, that would only result in a 5% increase in sales.