I started flying at 48 and flew for ten years. I am now 61 and was hired by two airlines here in England. Admittedly, I do look many years younger, but age is not an issue if you can do the job!
If you're interested, Delta is hiring now, so you may want to get your application in ASAP. Their last training date is May 2015.
The best thing about Delta is that they have no reserve; they simply have six "A Days" per month, which are the days you are on call. You can do all six at once or do three and three. Either way, it is a fair system as opposed to other major airlines in the U.S., where you are on reserve 8-15 years. So everyone at Delta, even new hires, hold a line.
A forum you may want to read which is very helpful, is DELTA AIRLINES 2015 ATLANTA F2F INTERVIEWS by Nelly - Flight Attendant Jobs - Page 240 | Indeed.com.