Originally Posted by
Hoi polloi
I wonder why we haven't focused more on improving sub-sonic designs? Most modern commercial aircraft fly at, what? Mach .80 to .85? Why not push to find that last remaining ~130 mph of sub-sonic speed in conventional designs while maintaining fuel efficiency?
It is expensive to do so and the time benefit is relatively small.
Boeing pitched the Sonic Cruiser concept to the airlines in 2001. It would have cruised as high as M0.98. Airlines preferred a more efficient, but slower, design which eventually became the 787 with it's M0.85 normal cruise speed.
https://en.wikipedia.org/wiki/Boeing_Sonic_Cruiser
Manufacturers can only build what their airline customers are willing to buy. That's why airlines are making small financial commitments to the Boom's Overture concept and proposed performance and economic targets.