1. Get Amex CC. Link

2. After miles post, and because you have the necessary CC to convert DL miles to cash, book a refundable ticket for more than $450.

3. Cancel the ticket within the same billing cycle. The cash over $450 comes back on your card, but the miles used are refunded as a DL e-cert, good for 1 year. $450 will better suit some peoples needs than 45K DL, which normally gets you 9/10 of a domestic RT. Link

Not a bad credit card sign-up bonus.

See delta.com under uses of miles for how the miles convert to an e-cert.

And if you were involved with Suntrust, you'd get an e-cert for $1700.