How good does your credit need to be to get an airmiles card?

I am 19 and i just got approved for my first credit card about 5 months ago. I use my card alot and always pay it off in full. I was just wondering how good my credit needs to be, and how long it takes to get good enough credit, to get an airmiles card?|||Good enough that you can buy airline tickets and pay your bills on time every month.