The planes with the lowest fuel economy are most desired, not those that fly faster.
I disagree, Its the low specific cost per unit distance that's important, hence CASM, Cost per Available Seat Mile, not Fuel per Available Seat Mile.
Fuel is the single largest cost over the life of an aircraft and it is this cost that mainly keeps airlines awake at night. What the jet costs is always lower than the fuel the airlines burns be it a lease or straight out acquisition. Thus, fuel efficient aircraft always beat aircraft that fly faster.
Fuel is often
the largest cost but that isn't to say that an increase in fuel due to flying faster cannot and is not more than offset by reduced labour, insurance, maintenance asset depreciation/leasing costs. A typical example of a medium to long haul direct operating cost breakdown(without airline overheads) would have about 40% of costs due to fuel 40-50% if the costs due to time based factors and the remaining 10-20% based on per trip/cycles factors.
This is still a high capex, low margin business and the cheapest way to fly will always beat the faster means of flying. Going faster means more thrust is needed, thus greater fuel burn.
I wont disagree that fuel burn per unit distance will increase when flying faster than maximum specific range speed but the increase in fuel burn can be traded against the time based costs to an optimum.
You are also probably right in that the cheaper means of flying beats the faster means however I think you have incorrectly made a direct inverse correlation between speed and cost. you can go faster AND
it be cheaper.
incidentally as you point out the high capital cost environment with relatively low fuel costs actually favors flying faster due to a bigger portion of the costs coming from time based sources.
if my optimum speed for fuel burn is M0.83 but by flying at M0.84 I spend an extra $100 on fuel for the flight but save $200 on crew costs and capital costs. As CFO which would you hope the planning department go for?
We have decades of data to fall back to.
Here is chart showing Type EIS vs Cruise speed. During the late 70s/early 80s (Fuel Crisis driving design?) we see a drop in cruise speed of new airliners only for it to rise again.
Airlines fly slower, have told OEM's that they want to fly slower, buy airlines that fly slower.
But yet that isn't happening? Curious.
These are the penny pinchers penny pincher we are talking about and even they have not seen a scenario where flying faster (without the tail winds) sees staff costs falling faster than fuel costs.
They do and they even have a setting for it in the flight planning ops, cost index. The optimal specific fuel burn is a tangential point on the speed vs drag curve from a point of zero speed. therefore as the time based costs vary inversely linearly with speed then there must be a point where the rate of change of fuel cost with respect to speed is lower than the reduction in cost due to time based influences. That's just Maths.
And we are not debating some marginal speed bump either because you do not need a whole new aircraft for that. It does not mean that airports are going to be more efficient, or that it suits bank systems either.
fuel efficient aircraft always beat aircraft that fly faster.
This is not true.
Airlines desire one thing and that is ever better fuel economy across the spectrum
They actually more closely desire is to maximise "Number_OF_PAX *(RASM-CASM)" The higher speed aircraft mentioned (Sonic cruiser and Concorde) were a play on the RASM part of this equation.
and smaller wide bodies in the upper end.
Is that a statement or an opinion?
If we get the NMA, it will travel at around mach 0.85 which is around what we generally see.
We would expect smaller (lighter) aircraft to fly slower at approximately W^(1/6) as described by Tennekes. The fact that we see it lower than this is likely to do with compressability effects. what we definately aren't seeing is slowing but a convergence toward ~0.85 at the larger end and ~0.8 at the narrow body end. It's hardly surprising that just as designs are converging towards the vanilla twin engined low mounted swept wing designs that the speeds are converging to an optimised point too.
To go something like mach 0.95, which would save time is largely a non starter.
Agreed, but airlines are not clamoring to go slower, which is what you said. The cruise speeds we have are already where they are because of optimisation of costs (which involves fuel) in the round. Unless fuel costs change dramatically then I cannot see a reason why the optimisations would fall very far from where they have landed today.
Outside of a very specific set of circumstances, under which an aircraft must already be en-route, an airline CANNOT save money by going slower than LRC.