Advanced Flight (Civ4)/Civilopedia

Little did the Wright Brothers know that less than four decades after their first plane touched down in the North Carolinian sand, aeronautical engineers would have already created a completely new way to power flight - the jet engine. This new engine, based on a turbine churning ultra-compressed air, lifted aviation to previously unreachable heights.
Applied to fixed-wing aircraft, the jet engine found its first application in World War II, powering the German Messerschmitt. In these machines, the jet engine increased speed by lowering the overall weight of the craft while providing a level of power unattainable in propeller-based engines. Modern jets, like the SR-71 Blackbird, are capable of speeds of over 2000 mph.
The jet engine would find further application in the creation of the helicopter. While Leonardo da Vinci had sketched prototypes of a rotary-wing aircraft in the fifteenth century, no powering mechanism until the advent of the jet engine could provide the proper balance of horsepower and low weight necessary to keep such a machine airborne. With the engine's incorporation into rotary-wing aircraft, it became possible for helicopters to take part in operations from combat to mid-sea rescue, rapidly making them some of the most versatile flying machines ever built.