Airborne wind energy aims to harness the potential of high-altitude winds that are hundreds or even thousands of metres above the surface of the Earth, using flying aircraft that are tethered to the ground. Wind movements at high altitudes (e.g. 500m+) are much faster than those close to the surface of the Earth and thus contain much more kinetic energy. Airborne system could, in principle, dynamically adjust its height and orientation to maximize its generation output over time, leading to higher capacity factors and better returns on investment. The various concepts that exist for airborne wind energy systems can be split into two groups: those where the electricity generator itself is airborne; and those where the flying parts of the system are used to mechanically drive a ground-mounted electricity generating station. Designs with a ground station generator are sometimes called “pumping kite generators” or, more simply, “energy kites”, because the airborne elements that drive the system typically have wing surfaces that resemble kites. Designs where the electricity-generating unit itself is mounted onboard a balloon or a flying wing are sometimes called “airborne wind turbines” or “fly-gen systems”. From a physics perspective, the size of the potential exploitable resource is very large, and the costs of the energy harvesting units themselves are potentially low because they are made of lightweight (but high technology) materials, which in principle makes for a strong value proposition. They also possess a strong competitive advantage in adding new potential resource extraction zones, with minimal needs for steel and concrete supports. A promising early niche application for airborne wind energy systems is believed to be providing power in remote locations where energy costs are already relatively high and the established competition tends to be diesel generators and solar power.