("George Patterson" wrote)
It's an urban legend, probably started because Eisenhower liked the idea.
It can be easily disproved simply by looking at a large scale map of I-40
or I-81 in mountainous terrain. Check Snopes at
http://www.snopes.com/autos/law/airstrip.asp
http://forum.keypublishing.co.uk/showthread.php?t=21093
(Scroll down for some interesting pics :-)
http://makeashorterlink.com/?N2E06234B
(One pic from the link)
http://makeashorterlink.com/?T5012334B
(Oops, there's a tank in our way...)
Montblack