(a) Investigations by U.S. military aircraft over Canadian territory will only occur in the case of an aircraft headed for the Canada-U.S. border from the Canadian side whose flight plan has not been transmitted to the U.S. authorities; or which is off course, and then only in the event that the actions of the aircraft give rise to a reasonable interpretation of intention to cross the border. Activities of Canadian military aircraft over the United States are similarly restricted.

(b) Close investigation, with all due precaution, or interrogation, is to be performed solely on unidentified multi-engined aircraft for the purpose of obtaining electronic or visual identification. No attempt will be made to order an intercepted aircraft to land, nor to open fire except when the intercepted aircraft is over the national territory of the Air Force performing the interception.

(c) Investigating aircraft will not approach closer, in accordance with Civil Aeronautics Authority and Department of Transport standards, than is necessary to establish identification.

2. At the PJBD meeting of June 1952, the U.S. Air Force Member stated the opinion of the USAF that Recommendation 51/4 was too restrictive. The terms proposed as more suitable by the USAF are as follows:

"(a) The Air Defense Commander of either country, or the coordinated air defense system of both countries, be authorized to employ fighter-interceptor aircraft of either or both countries, or other means of either or both countries, available to him in the interception of unidentified aircraft over the national territory of either country regardless of International Boundary.

(b) The exercising of this authority be qualified by the following conditions:

(i) Investigations to occur in, but not limited to, the case of aircraft crossing an Air Defense Identification Zone Boundary (Canada or the United States) whose flight plan has not been received by the Air Defense System, or which was off course or late beyond mutually acceptable criteria for identification. Investigations be conducted by interception and visual identification, and electronic interrogation.

(ii) No attempt be made to order intercepted aircraft to land nor to open fire unless the aircraft commit(s) a hostile act, is (are) manifestly hostile intent, or is (are) declared hostile by the Air Defense Commander responsible for identification.

It will be noted that these provisions make no attempt to define 'hostile act' and 'manifestly hostile intent.' It is considered to be impracticable to attempt to list or otherwise define all of the many ways in which an aircraft can commit a hostile act or evidence hostile intent. Any agreement specifically spelling out such methods would be too restrictive upon the Air Defense Commander concerned."

3. The question of the exact meaning of the USAF proposals has been discussed by this Department with officers of the RCAF concerned with the matter. They have advised that if the proposals were approved it would mean that either USAF or RCAF aircraft, directed either by a USAF or RCAF air defence controller, could order interception of aircraft over U.S. or Canadian territory, and if it was deemed that a hostile act was being committed or intended, could order the aircraft being intercepted to land or be shot down. It would remove the present restriction that no attempt will be made to order an intercepted aircraft to land, nor to open fire except when the intercepted aircraft is over the national territory of the Air Force performing the interception.

4. The U.S. proposals were referred by the Secretary, PJBD, to the Department of Transport for comment. The Deputy Minister of Transport replied, on July 21, 1952, that he could see no reason for extending the existing regulations. He followed this by two further letters, the first dated July 21, 1952, and the second dated July 22, 1952, (copies attached)^? giving details of an incident involving a TCA flight from Winnipeg to Toronto, on July 9, 1952, when it was intercepted by two USAF F6 aircraft. In his letter of July 21 he stated that he regarded this incident as supporting the argument that the existing procedures should not be extended as proposed by the USAF.

5. Copies of the letters received from the Deputy Minister of Transport have been passed to the RCAF member of the PJBD for comment. In the event that the USAF aircraft violated existing procedures, the A.O.C. Air Defence Command, RCAF, has an established channel for reporting the incident to the USAF for disciplinary action.

6. The RCAF officers concerned have informed us that flight plans of all aircraft flying in the air defence interception zone at altitudes above 4000 ft. are required to be transmitted to air defence control centres both in Canada and the United States. In Canada the communications links involved are operated by the Department of Transport, and in the United States by the Bell Telephone Company on behalf of the Defence Department. The air defence identification zone in Canada has only recently been extended west of the Great Lakes, and links with the USAF are not yet functioning satisfactorily. The RCAF therefore anticipates the possibility of further interceptions until the situation is remedied. This will likely be a source of irritation to TCA and the Department of Transport, but should probably be tolerated for the time being so long as the intercepting aircraft obey the established procedures. The RCAF officers concerned ventured the personal comment that the Department of Transport was not being very helpful in making the present system function effectively.

7. After the Services and the Department of Transport have settled on their views with respect to the U.S. proposal, I will consult with you prior to the September meeting of the PJBD as to the position to be taken by this Department. In the meantime I thought that you would wish to be informed of the existing situation and the incident involving the TCA Flight from Winnipeg to Toronto.¹⁰

M.H. WERSHOF