You do not need an affinity credit card in order to belong to a frequent flyer program. Many people do not have credit cards, but get miles for flying the airline. Just go to aa.com, and united.com and sign up. You will then be members of their frequent flyer programs and get miles for flying their airline. If you then apply for a credit card, you would put in you exisitng ff# to be attached to that credit card. It does not cost anything to belong.