Explain why some planes fly faster than others?

Power and type of propulsion

To put it simply, the more thrust or power you have in an engine, the faster your airplane will go. Propeller planes perform well at low to medium speeds, but if you're looking for high speed, the best option is jet engines. When a plane uses a jet engine, it burns fuel quickly, creating an ultra-powerful airflow backward, propelling the aircraft forward at high speed. If you really want to go even faster, you can switch to scramjet engines or afterburning jets typically found on supersonic military aircraft, which burn more fuel but push the limits of speed by producing very intense thrust. It all depends on the type of engine and its ability to provide high thrust over a long period: it makes a huge difference in your final speed.

Advanced aerodynamic design

Planes designed to go faster are shaped very precisely to glide better through the air. This is referred to as advanced aerodynamics. The idea is to minimize aerodynamic drag, the invisible resistance that air opposes to motion. The more streamlined the aircraft, the better it slices through the air, similar to a fish that glides easily in water thanks to its streamlined shape. Elements such as the sharpened nose, the streamlined fuselage, and smooth surfaces play a huge role in allowing the aircraft to move swiftly without wasting its power. There are also tricks like specially designed air intakes to avoid disturbances that slow the aircraft down, or wings specifically designed to reduce turbulence and friction. All these small details significantly reduce the resistances encountered and allow the fastest planes to reach very high speeds without unnecessarily wasting their fuel.

Materials and weight of the aircraft

The lighter the aircraft, the more easily it reaches high speeds. Today, fast airplanes are often built from materials like carbon fiber composites or very light aluminum alloys. These materials significantly reduce the structure's weight while maintaining excellent strength. Less weight means less drag, less energy required, thus more speed and efficiency. In the era of the first jet aircraft, steel was quite common, but frankly too heavy. Today, the focus is primarily on finding the perfect balance between robustness, lightness, and the ability to withstand the intense stresses of high-speed flight, all while ensuring maximum safety.

Wing configuration and geometry

The shape and arrangement of the wings significantly influence an aircraft's potential speed. For example, swept-back wings are often used to reduce air resistance at high speeds, making planes faster. A high sweep angle allows the aircraft to glide better through the air by delaying aerodynamic disturbances. In contrast, a straight wing is ideal at low speeds, providing more stability and better lift, but it quickly reaches its maximum speed limit. There are also variable geometry wings, like those on some military jets, capable of changing angle to easily transition from low speed to supersonic speed. Finally, the thickness of the wings also matters: the thinner the wing, the less resistance it encounters at high speeds, allowing the aircraft to accelerate more efficiently.