Saving fuel and range flying slower?

[Shaun Patterson]

Altitude is a major factor here; for instance a CRJ700 travelling at Mach 0.78 (economic cruise speed) at 27,000ft uses around 5-10% more fuel than at Mach 0.78 at 33,000ft. While the indicated
airspeed at a higher height is lower, the ground speed tends to be higher.