The actual figure depends on so many questions - including what what you mean by power setting...
Another way of expressing it is fuel flow - a typical aircraft like a A320 might burn 1200kg per hour per engine in the cruise - whereas at take off power fuel burn might be about 2500kg per hour per engine. At cruise altitudes engines produce a lot less power than they do at sea level - but they work more efficiently.
The specifications for the 737 NG include a line in the performance table specifying "Cruise Max Thrust" - I have never noticed this before.
The actual figures are 5,960 lbf (at FL350, mach 0.8) which is only 22% of the rated take-off thrust for a CFM56-7B....
The fuel consumption does not decrease linearly, but you get very roughly a third of take-off fuel flow in the cruise.
The reason for lower thrust is lower mass flow due to lower air density in the cruise. Plus losses because the difference between exhaust velocity and engine velocity is much smaller than standing still on the ground.
Many thx to both you and nmcalba for clarification.
In laymans terms it seems comparable to a carburettor fitted to a car engine. This is designed to mix fuel & air, with the passage of the air helping draw the fuel into the inlet (unlike fuel injection, where the fuel is "injected" into the air flow/ directly into the cylinders). If this car engine was taken to altitude, the air flowing through the carb would be thinner, and hence the "draw" on the fuel flow reduced - which is just as well because without sufficient oxygen, any "extra" fuel would remain unburnt and wasted.
(meh - it's not entirely accurate, but something I have in my head that non-av persons might relate to)
Likewise with a jet engine, there is little benefit to adding more fuel if the oxygen isn't available to combust it efficiently. Although the makers of the Convair Cv990 probably thought differently.
As regards "losses because... exhaust velocity vs engine velocity..." I am reminded that the RR Olympus engines on Concorde were reckoned to be the most efficient engines of their generation precisely because Concorde was already travelling at Mach 2 !
Indeed, nmcalba comments thus...
...although overall the engine is working more efficiently in terms of work done vs fuel burnt.
- which leaves me in a conundrum.
p.s. I don't doubt your numbers, or your expertise. I'm just puzzled by the contradictions....
Maybe one day it will all drop into place, probably in the final moments of life as I drift off into oblivion.
Nothing to see here; move along please.