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Old 22nd Nov 2021, 18:25
  #16 (permalink)  
Join Date: Jul 2013
Location: Everett, WA
Age: 67
Posts: 3,628
Anyone else remember the Boeing "Sonic Cruiser"? It would have cruised at Mach 0.95+, with costs/mile equivalent to a 767 - so about 20% faster than the Mach ~0.82 design cruise speed of the 767. After a lot of initial excitement, the whole concept was dropped because the airlines decided they'd really rather have an aircraft that flew about the same speed as a 767 but with ~15-20% lower per mile costs. There simply are not a lot of people who are willing and able to spend a large premium to get there a few hours sooner. Biz jets are a little different - the people who fly on biz jets generally are not too worried about costs (if they were they'd fly commercial), although like Less Hair I question if the potential market is large enough to even begin to justify the investment.

As for cruise speeds, although there were a few outliers in the early jet age that went faster (which were commercial flops), most longer range jets cruise in the Mach 0.80 to 0.85 range and it's been that way since the '60's. The 747 was originally designed to cruise at 0.87, but the fuel burn went up so fast between 0.85 to 0.87 that few ever actually operated it that fast - it just wasn't worth it.
As MarkerInbound notes, part of it may be the statistic affect of the proliferation of smaller aircraft such as the 737 and regional jets (although the NG/MAX is faster than the classic 737, it's still basically sub 0.80 cruise).
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