Airbus A380

Boeing did spend about 5 years, and millions on several concepual designs for a super jumbo. but finally decided the market would not be enough to repay the multi-billon $ cost of an all new design, particularly once Airbus announced they would also be building one. the have considered and done some early model testing for streching the the upper deck on the 747 even further back (it has been enlarged several times since the original model) but seem to have put that idea on hold (the Bump area was originally for first class seating, (but due to the hull curve it was uncomfortable), so it was converted to first class lounge (still not too popular) many airlines now jam the super cheap seats up there)