In 1949, Canadair recognized that the RCAF would soon be looking for a replacement for the Avro Lancasters being used in the maritime patrol role and proposed the CL-29, a variant of the North Star, itself a variant of the Douglas C-54 Skymaster or DC-4 transport. When the RCAF issued the specification in 1952, it was for a larger and more capable aircraft, and two proposals were received. These included a Lockheed Constellation variant from Lockheed, however its low speed handling was deemed inadequate by the RCAF, while Bristol proposed a variant of their Britannia airliner but concerns were raised over its floating controls, where they were controlled via servo tabs rather than direct linkages. The RCAF preferred the Bristol proposal, but it would be developed in Canada. Canadair presented two proposals, the CL-28 also based on the Britannia, which was accepted, and a lowest cost design called the CL-33 which was described as a fat Lancaster. It would have comparable to the Avro Shackleton already being operated by the RAF, but significantly lighter, and was to be powered by the same engines as were used in the CL-28, or similar radial engines.