Which type of wind aids in accelerating an aircraft's groundspeed?

A tailwind aids in accelerating an aircraft's groundspeed because it blows in the same direction as the aircraft is flying. When an aircraft benefits from a tailwind, the speed of the wind adds directly to the aircraft's airspeed, resulting in a higher groundspeed.

For example, if an aircraft is flying at an airspeed of 150 knots and encounters a tailwind of 20 knots, its groundspeed will be 170 knots. This increased groundspeed can result in reduced travel time and fuel efficiency benefits during flight.

In contrast, a headwind, which blows against the direction of travel, would decrease the groundspeed, while a crosswind would not significantly impact the groundspeed since it affects lateral movement rather than forward motion. Downwind can be confusing, as it might imply movement with the wind, but in aeronautical terms, it often refers to being on a specific leg in the traffic pattern rather than the wind itself affecting speed.