What is a "cross-country flight" in gliding?

A "cross-country flight" in gliding refers to a flight that involves traveling between two or more defined points, typically covering significant distances. This type of flight often requires careful planning and navigation skills, as the pilot must consider various factors such as weather conditions, airspace restrictions, and the availability of suitable landing sites along the route.

In cross-country flying, pilots utilize their skills in soaring by using thermals, ridge lift, and other atmospheric phenomena to gain altitude and make progress along their chosen path. It differs significantly from other forms of soaring, such as flying in circles, which may be aimed at staying within a small area to take advantage of local lift sources. The altitude constraint of 10,000 feet or the necessity of having a co-pilot does not define a cross-country flight but rather relates to other operational protocols or regulations in aviation.

In essence, the foundational aspect of a cross-country flight is the ability to navigate over varying distances and terrains while effectively utilizing the glider's capabilities for soaring, making option B the most accurate definition.