Series consists of Transport records created with a security classification of "Confidential" or higher. They form part of the Central Registry operations, but were maintained physically separate within the department, and belong to a different filing system. The file numbers range from 11 to 999. This subject classification scheme was phased out in 1984-1985.
Many of the files were created during the Second World War and reflect the co-operation between the Departments of Transport and National Defence, particularly with regard to the training of air crews in the British Commonwealth Air Training Program, meteorological and radio services, the creation of the Merchant Marine, censorship, prisoners of war, honours and awards, construction and maintenance of airports and trans-Atlantic air and marine services. Post-war files relate to Transport Canada's responsibilities with respect to air, marine and surface transportation including interdepartmental conferences and committees, international affairs, high-level policy procedures, and Joint United States-Canada defence issues.
The classified central registry was broken down in the following broad subject categories: block 11 - Defence Measures and Regulations ( vols. 613-644, 1066-1102 2300, 2156-2158, 2352-2357, 2398-2399, 2401-2402); block 12 - Transport of Troops and Supplies (vols. 644, 859, 1102-1105, 2156); block 14 - Joint United States and Canada Defence (vols 645-654, 1105, 2357, 2368, 2399-2400, 2402-2410); block 16 - Post War Issues, including files spanning the period of the Second World War (vols. 655-659, 659-660, 1105, 2178, 2400, 5087-5101); block 18 - Honours (vols. 1105-1107, 2185); block 19 - Bermuda Conference (vol. 3142); block 22 - Air Services (vols. 660-667, 2357-2358, 2400, 2411-2412); block 24 - Marine Services (vols. 667-669, 1108-1110, 2400); block 26 - Wartime Transport (vols.1100, 2401); block 28 - Conferences (vols. 544-546, 669, 673, 1110, 2401); block 31 - Facsimile (vol. 673); block 32 - Australian and Orient Press (vol. 3142); block 34 - Legislation (vol. 2401); block 38 - Railways (vols. 2401-2402); block 40 - Highways (vol 2402); block 100 - Arctic Transportation Conference (vol. 2633); block 102 - Security (vol. 2633); block 104 - Conferences and Committees (vols. 2182, 2362-2364, 2595-6, 2633-4, 2785-6); block 105 - Interdepartmental Committee on Water (vols. 2596, 2635-6, 2773-4, 2786); block 106 - Interdepartmental Committee - Air (vols. 2412-3); block 112 - NATO (vol. 2786); block 155 - Legislation (vol. 1809); block 200 - Officers and Employees/State Visits (vols. 2361, 2601); block 202 - Site Selection (vol. 2795); block 204 - Emergency Planning (vol. 2787); block 206 - International exchanges (vol. 2787); blocks 260 and 266 - Collective Bargaining (vols. 2788-2792); block 520 - Air Services (vol. 1602); block 552 - Trains (vol. 2636); block 666 - Aviation - Foreign (vols. 2392-2398); block 700 - Telecommunications (vol. 2414); and block 702 - Commonwealth Telecommunications Board (vols. 2353, 2367).
Volumes 4147-4176 contain classified registry files relating exclusively to marine casualty investigations. Prior to 1985, records of marine inquiries designated "confidential" were placed in the classified registry system (500 file block). These files are similar to the records found in the central registry system (9704 file block) except for their security classification status.