Many people use Amex's Bluebird card (a prepaid card that can be loaded with Vanilla Reloads) as a means of managing funds and generating miles. A common tactic is to purchase reloads with a miles earning card, load the funds to Bluebird, and pay that (or another) credit card bill from Bluebird's bill pay service. However, sometimes it's easier to simply withdraw the funds to your linked checking account, an option that Bluebird has always allowed.
However, since Bluebird keeps "improving" its site, the link for withdrawing money has moved around a bit. Well, the latest iteration moves the link again, but this time it's much easier to find. Now you simply log in and click the "My Account" tab at the top of the page: