"The testing of cruise missiles in Canada proved very contentious. The government explained its decision in both political and technical terms. Politically, testing demonstrated alliance solidarity over the modernization of NATO's nuclear deterrent. Technically, testing the missile over terrain similar to that of the northern Soviet Union would improve its effectiveness, and allow the North American Aerospace Defence Command (NORAD) to develop an anti-cruise capability. The tests would take place in a 2,200-kilometre test corridor that included parts of the Northwest Territories, British Columbia, Alberta and Saskatchewan. Tests could involve either releasing the missile in a "free flight" to its target, or allowing its guidance system to direct both the missile and the launch aircraft to the target in a "captive carry" test. The tests take several hours, and involve a number of aircraft in both Canada and the United States, from tankers to fighters to Airborne Warning and Control System (AWACS) planes. After the first few years of tests, attention shifted from monitoring the missile itself to attempting to track and intercept it. In order to simulate the climate of the northern Soviet Union, most cruise missile tests in Canada have taken place in the winter months."