So you want the B of A US Air card with your current credit limit, and you want to maintain your credit history by showing a long standing card. Simple. Just open the new US Air card on line, and don't close your current card. There is no reason why you can't have both cards. Then, after you receive the card, ask to transfer whatever part of the credit limit you have on you old card to the new card. They have done this for me several times in the past. The trick is to first have the new card.

Unlikely: If for some reason you are denied the new card, perhaps because B of A says they have given you enough credit limit already, then ask to talk to someone in the credit department and tell them you want to use part of your credit limit on the old card for the new one. An appropriate phone number will probably appear on the letter saying you have been denied the card. This has happened to me only once, and only with Citibank, when I had credit limits on cards from them well exceeding my annual income and was using much of it for 0% balance transfer offers. The phone call got me the card I wanted.

Are you sure you want the B of A US Air card. Consider instead the Juniper Bank offer, with no annual fee for 2 years plus 50% more miles for purchases the first year.

Be sure to get the best offer for whichever card you want (or both, for that matter). Currently you can get 25,000 miles for first purchase plus $25 for the B of A card, and 15,000 miles for first purchase for the Juniper card.