The Canadian-United States Military Co-Operation Committee (MCC) devised this plan in 1946 for the air defense of North America. Each country was represented by the military and diplomatic members of the Permanent Joint Board on Defence, including representatives of the various armed services and, in Canada's case, the secretary of the Cabinet Defence Committee. The two civilian chairmen of the PJBD were exluded. The plan (not terribly well thought out at this stage, but still an important indicator of governmental thinking and policy) shows that US and Canadian concerns in the immediate postwar years were centered solely on Soviet attack.
Canadian member of the MCC E. W. Gill, secretary to the Cabinet Defence Committee and a staffer in the Privy Council Office, wrote:
"I have regarded the Committee as the drafting group whose members reflect the views of the chiefs of Staff in the drawing up of their plans. There is evidence that this consultation between planners and chiefs takes place on the U.S. side, but is entirely absent on the Canadian side. I think it is safe to say that at no time since the planning started have the planners... received any guidance from their chiefs as to how they should proceed on each phase of the plan. As a result, the planners have a free rein and are producing plans which must be "sold" to their superiors. The committee has thus become a pressure group in which the services combine to put up as strong a case as possible to their respective chiefs and Governments. In this rather doubtful role we are subject to the machinations of the U.S.... The obvious intention of the U.S. services [is] to use the plans... as a basis for securing appropriations from their government." [Memo from Gill to A.D.P. Heeney, Report on MCC Meeting at Trenton, 22 - 25 July 1947. Privy Council Office Records, Public Archives of Canada, RG 2/18, vol. 74]
The Canadian government concluded that the MCC proposals, with their JCS imprimatur, and without any disagreement from the State Department's representative on the MCC, reflected U.S. policy - despite the fact that it was absurd to think that the Truman administration, in the midst of demobilisation and still committed to rapidly reducing defence budgets, would suddenly reverse course and create Fortress America by 1950.
Why would the JCS go along with such a grandiose plan? According to historian Joseph Jockel, "Mostly because they were not paying much attention. The entire military establishment in Washington was in turmoil as it coped with demobilization and internecine struggle. There was no overall strategic plan." General Guy Henry, the senior US Army member of the PJBD, later complained that "It took considerable work on my part to obtain actual concrete comments... from the Commanding General of AAF and the Plans and Operations Division of the War Department." As Jockel correctly notes, the "AAF Air Defense Command was making the same complaints about plans and pleas it was submitting to Washington."
Of particular relevance to the Aztec case (and Roswell, too) are two points:
1. The disarray in military thinking about continental air defense in the late 1940s; and
2. The fact that, in those plans which were drafted in 1946 to 1949, no specific thought was given to the defense of American atomic energy installations; rather, the concern was with creating a de facto "picket line" around the continent, which could detect Soviet attacks.
This runs contrary to the claims of Aztec proponents that there were Top Secret radar bases in place as early as 1946 to protect AEC installations in New Mexico.
See Joseph Jockel, No Boundaries Upstairs: Canada, the United States, and the Origins of North American Air Defence, 1945 - 1958 (Vancouver: University of British Columbia Press, 1987), perhaps the best study out there of the subject.