Electric motors for airplanes are much lighter and more compact than comparable internal combustion engines. Their power output is limited by rpm and cooling. Advancements in batteries, motors, and motor controllers have led to some practical production electric propulsion systems for some ultralight applications. Ultralights are a good application for electric power as some models are capable of flying with low power, which allows longer duration flights on battery power. ^{flyingmag.com 1 2}