What significant aviation innovation was developed during World War I?

The development of the interrupter gear during World War I marked a significant innovation in aviation technology. This mechanism allowed pilots to synchronize the firing of their aircraft’s machine guns with the rotation of the propeller blades, ensuring that bullets did not strike the propeller while it was in motion.

Prior to this invention, it was challenging for pilots to effectively engage enemy aircraft without damaging their own propellers. The interrupter gear solved this problem by timing the gunfire precisely so that it occurred only when the blade was not in the line of fire. This technological advancement greatly enhanced the lethality of fighter aircraft and was crucial in establishing air combat tactics during the war.

The other options, while important in their own right, were not developed during World War I. Turbojet engines came into play much later, during World War II. Radar technology did not see significant development until the late 1930s and into World War II. Pressurized cabins became common in the post-war era, greatly improving the safety and comfort of high-altitude flights but were not present during World War I.