How does altitude affect an aircraft's fuel consumption?

Higher altitudes contribute to more efficient fuel consumption primarily due to the reduction in air density. As an aircraft ascends, the air becomes thinner, which results in decreased drag. This reduction in air resistance allows the aircraft to maintain its speed using less power, and therefore, burns less fuel for the same amount of distance traveled compared to lower altitudes where the denser air increases drag.

Additionally, at cruise altitudes, engines may operate more efficiently because they can take advantage of the cooler temperatures, optimizing performance and further reducing fuel consumption. The combination of these factors demonstrates why higher altitudes can lead to improved fuel efficiency.

The other responses present inaccuracies regarding fuel consumption at various altitudes. While it's understandable to think fuel consumption might increase at higher altitudes due to other factors, it is clear that the primary effect is a beneficial decrease in drag, leading to overall efficiency gains when flying higher.