And, in fact, the only time that Article 5 of the NATO treaty -- the mutual self-defence article -- has been invoked was after 9/11, when the US used it to drag the rest of NATO into Afghanistan.

The article says:

" Five NATO planes have arrived at Tinker Air Force Base in Oklahoma City, Oklahoma"

and:

"Most of the United States' 30 AWACS, based at Tinker, have been flying around-the-clock surveillance of U.S. airspace..."

In my opinion, the phrase, "a good chunk of" is dubious. In a few minutes of Googling, I could find no indication of how many missions (if any) those NATO planes flew.

http://www.nato.int/docu/review/2006/issue2/english/art2.htm...

Fred Kaplan:

"Aside from letting a handful of NATO's AWACS radar planes come help patrol American skies, Bush's response was a shockingly terse: Thanks, but no thanks; we'll handle it by ourselves. Marc Grossman, the undersecretary of state for political affairs, later admitted to the Washington Times that the United States initially 'blew off' the allies. Douglas Feith, the undersecretary of defense for policy, said that the United States, in the Times' words, 'was so busy developing its [Afghanistan] war plans that it did not have time to focus on coordinating Europe's military role.'

"The effect, of course, was to alienate the allies just as they were rediscovering their affections. As London's conservative Financial Times later put it, 'A disdainful refusal even to respond to a genuine offer of support from close allies, at the time of America's most serious crisis in decades, spoke volumes about its attitude to the alliance.'"

http://www.slate.com/id/2088113/pagenum/all/

(The similarity between the "thanks but no thanks" phrase used by Kaplan and the one used by me is a complete coincidence. I found this article this afternoon when googling for something to support a rebuttal.)