Montreal, what you'll have to do is break the page out of the frameset it's in (http://www.flyertalk.com/milesfr.shtml).

To do this, right-click (or control click for Macs) on the thread page you want to bookmark. When the menu pops up, choose to open that page/frame in a new window. This will cause the page you want to break out of the frameset and into a new window. Bookmark this new window and you should be set...