Both AA and FedEx have potential trouble on the horizon. I think AA would provide the most stability over the next 20 years of your career however. And if you came to AA now, you would have a ton of pilots beneath you in just a few years. How many would you have beneath you at FedEx?
I have several friends at FedEx and they love their job. I have several friends at AA and they also love their job. Pick whichever one works best for you and your families needs.