Sorry... Diners won't have me, so I refuse to recognize them.

I don't think you'll see a co-branded Signature card. Reason being is that Visa requires the issuer to provide airline rewards (i.e. tickets). If a co-branded Signature card were issued, the case could be made that the issuer not only had to provide FF miles for dollars spent; but also would have to offer Signature Card travel points (a double-dip, if you will). That wouldn't be too cost effective.

Having said all of that, it's impossible to rule out any possible scenarios since this business is even more competitive than the airlines! For example (purely hypothetical), if you had a Citibank/AA Platinum card and you wanted to upgrade to a Citibank Signature card (but didn't want to lose the miles); Citibank could conceivably 'link' the two accounts and continue to post AA miles based on the Signature card charges. I think you'd have to be a very profitable customer for them to do that (i.e. revolve a large balance, pay big interest).

Typically, Amex and Diners charge much higher fees to merchants for the privledge of accepting their cards. Between that and the annual fees charged, those card programs are able to buy miles from the airlines and give you a choice.

The co-branding arrangements between issuers and airlines, auto makers, etc. often make a decent profit (or at least break-even) for Visa and MasterCard issuers (always depends on the deal). That's why they are even able to offer such programs given the economics.

FYI, I don't work for a credit card company. We make the software that make the things work.

Cheers,

'toad