Have to agree with M(F)S, the BD500 is just the basic Bombardier Type Number registered with Transport Canada. Believe the fuselage would be getting so long as to have definite problems with tailstrike during takeoff. The other possible consideration is that BA contracted with China several years ago to help with all aspects of testing and certification of the C919 - essentially a wider-bodied CSeries rumoured to use the same wing and many of the systems.