during the tests which involved 6,000 sorties flown by air forces from the U.S. , UK and Canada simulating Soviet fighter / bomber attacks against New York , Chicago and Washington . This made it the largest military aviation exercise ever held.   http://www.airspacemag.com/history-of-flight/this-is-only-a-test.html   http://en.wikipedia.org/wiki/Operation_Skyshield   We went on alert, of