Jonas,

At some point you'll reach a point of diminishing returns. As
speed decreases induced drag increases and you need to increase power
to maintain altitude/speed. Most jet aircraft have a maximum cruise
power, long range cruise power and intermediate cruise power setting.
Intermediate gives the best time to burn ratio, but if your prime
concern is fuel savings and extended range, then you could fly at the
LRC setting, which, in some aircraft, could yield up to a 15% increase
in range. The expense, though, is flight time.

P.

(Jonas Heisenberg) wrote in message om...
Hi all.

Looked around a bit for fuel efficient (big, commercial) airplanes.
The best ones I found were the Tupolev TU-330 and the Antonov AN-70.
They had cruising speeds/fuel consumption of 780-850 km/h and 118-125
g/t-km. Now my question: would lowering the cruising speed to e.g.
300-400 km/h make them more efficient?

Thanks, Jonas