The Avro Arrow is a bit of Canadian mythology - it was an interceptor that was cancelled in the late 50's that Canadians lionize because it was better than what the US and UK were using at the time (at the time being the keyword there).

By all accounts it was a solid interceptor and could break Mach 2 (with one model aiming for Mach 3). But at the time we were becoming less concerned with bombers carrying nuclear payloads and more concerned with ICBMs so the program was cancelled and all models destroyed (except for one that was hidden away, according to the myths).

In truth it might have been a high end interceptor, and the designers certainly knew what they were doing (after cancellation a lot of them went south and got jobs working for US aerospace contractors. It was certainly a fine attempt given Canada's limitations (fewer people means fewer skilled designers and engineers to build the thing). But A couple years after the Arrow was cancelled the US launched the F-106, which had superior qualities to the Arrow (as it existed, not as might have been with the Mach 3+ model) across the board.