At a slowing speed and typically at near-idle thrust. The aircraft exchanges gravitational potential energy for velocity through most of the descent.
The only high-trust portions are when reverse thrusters are engaged, typically for a few seconds following landing, or if TOGO power is invoked for an aborted approach.
Which is effectively level flight / continued cruise, a low-power flight segment, not a high-powered one. That last would only apply if the aircraft had aborted an approach, which typically gives priority.
Again: the original claim was that both take-off and landing were high-fuel-consumption flight segments. That's untrue. Under normal conditions only take-off is, and even most deviations from a nominal approach have a fairly minor impact.
You're going to extreme lengths to avoid admitting this, and are making the issue personal to boot. Any particular reason for that?
The slowing isn't using gas - its not like they put the plane in reverse to slow it down. They're descending and trading potential energy for energy to maneuver at low altitudes. The thrust is near idle.
True, but not every approach to an airport is a nice constant vector.
Continuous descent operations are the optimal, but there's plenty of suboptimal airport approaches that require level flight at a height where fuel efficiency is far less than at cruising altitude.
Do you have any statistics to say it happens so often that airplane landings are so suboptimal that they use anywhere near climbing fuel rates and times that it matters to the overall discussion? It seems unlikely to me.
Though yes, take-offs add considerably to the consumption. Landings don't, as aircraft are typically gliding in at or close to idle thrust.
Efficiency for very-long-range flights is actually reduced as total take-off weight (TOW) must be reduced, exchanging payload (passengers) for fuel.
For very short flights, fuel burn is about 10l/100km-passenger. At intermediate ranges, that falls to about 3l/100km-passenger. See:
https://www.fzt.haw-hamburg.de/pers/Scholz/arbeiten/TextBurz...