I went back to the Wikipedia page "Airmail" and noted that someone had deleted the link that I created under "External Links."  So I guess the technique that Jamie used on that page to get to the AAMS site is the best we're going to be able to offer, but I plan to go through the process of adding the link one more time.  I added external links to the AAMS site on two other Wikipedia pages, "Airmail Stamp" and "First Flight Cover," so we'll see if those links remain on the pages.