Some credit cards seem to be extremely good at recognizing patterns and using this to decide whether there's reason for a security concern. It's too bad that DL doesn't have the same ability to somehow note that your purchases of SDQ tickets in your name and with the same credit card attached to your DL FF account and in your own name should not cause alarm. In fact, IME AmEx does this very well and doesn't give me problems, although I do try to call to advise them of trips to weird places that are new for me.