What procedure should be followed to achieve minimum fuel consumption for a given cruise leg in adverse wind conditions?

Increasing speed for a headwind is a critical consideration for minimizing fuel consumption during a cruise leg in adverse wind conditions. When flying into a headwind, the aircraft's groundspeed is reduced, which can extend the flight time and increase fuel burn due to prolonged exposure to the adverse conditions. By increasing the speed, the aircraft can better maintain an efficient groundspeed, reducing the duration of flight in the headwind and ultimately conserving fuel.

Furthermore, maintaining a higher airspeed in a headwind allows the aircraft to effectively counteract the drag and lift losses typically associated with adverse winds. It's important, however, to ensure that this increase in speed does not exceed the aircraft's operating limits and is balanced against the potential for increased fuel flow at higher power settings.

While other options may seem reasonable, they either don't address the nuances of optimizing fuel efficiency in varying wind conditions or could lead to increased fuel consumption. Thus, adjusting the speed in response to the headwind is a strategic choice aimed at minimizing fuel consumption during the flight.