That 78 year old flight attendant -- I believe her name is Juanita Charmichael. My father used to fly with her, she is a wonderful woman and a very hard and dedicated employee to American Airlines. We could all learn a lot from such a devoted and intelligent woman.
As far as getting hired by the airlines goes... I would recommend looking at http://www.flightattendantcareer.com
for some advice. The sight is run by an AA flight attendant who wrote a book on how to get hired. The first time I interviewed with AA I was turned down, the second time I was interviewed I decided I would read her book and THEN interview... that times I was hired. It's a great book with all the questions and answers in it. I highly recommend it.
I have very little customer service experience, but I do have a bachelor's degree in communication and am almost done with my master's degree in communication as well. I think they are looking for someone who is well rounded, outgoing, intelligent, and comitted. They want to see that when you start something, you finish it -- like college for example. They want to see that you haven't had a lot of short-term jobs, that you are a long-term employee with long term goals.
Overall, I would say age is not a big deal to them -- they are going to care about the person that they see in the interview. That is where you have to shine. Everything else is black and white. For example, all the application stuff is just do you have it or don't you... everythign is very cut and dry. However, in the interview they are very subjective. They are looking at a number of different variables that you need to be aware of. If you are granted an interview (at AA at least) they will hire you the same day you interview if they like you. You have to be focused on customer service, demonstrate your ability to listen to instructions, listen to others, and to speak at appropriate times and appropriate lengths. That is my experience anyway.
Good luck to you,