While the standalone bucket checker you have posted is a nice tool, it does not provide accurate information for US domestic flights.
As far as I know, the only tool currently available to perform this function is at Amex's travel website, ITN (
http://www.itn.net).
Virgin Flyer's bucket checker was superior because it was accurate, it did not require the user to login, and the check could be performed with a minimal number of steps.
Please bring back the Virgin Flyer bucket checker!
Edited to add: Should have posted under the Website topic.