In 1942 Adolf Galland—director general of fighters for the Luftwaffe, veteran of the Battle of Britain, and one of Germany's top aces—flew a prototype of one of the world's first jets, the Messerschmitt ME 262. "For the first time, I was flying by jet propulsion and there was no torque, no thrashing sound of the propeller, and my jet shot through the air," he commented. "It was as though angels were pushing." As Adolf Galland and others soon realized, the angels were pushing with extraordinary speed. The ME 262 that Galland flew raced through the air at 540 miles per hour, some 200 mph faster than its nearest rivals equipped with piston-driven engines. It was the first operational jet to see combat, but came too late to affect the outcome of the war. Shortly after the war, Captain Chuck Yeager of the U.S. Air Force set the bar even higher, pushing an experimental rocket-powered plane, the X-1, past what had once seemed an unbreachable barrier: the speed of sound. This speed varies with air temperature and density but is typically upward of 650 mph. Today's high performance fighter jets can routinely fly at two to three times that rate.
The jet engine had a profound impact on commercial aviation. As late as the 1950s transatlantic flights in propeller-driven planes were still an arduous affair lasting more than 15 hours. But in the 1960s aircraft such as Boeing's classic 707, equipped with four jet engines, cut that time in half. The U.S. airline industry briefly flirted with a plane that could fly faster than sound, and the French and British achieved limited commercial success with their own supersonic bird, the Concorde, which made the run from New York to Paris in a scant three and a half hours. Increases in speed certainly pushed commercial aviation along, but the business of flying was also demanding bigger and bigger airplanes. Introduced in 1969, the world's first jumbo jet, the Boeing 747, still holds the record of carrying 547 passengers and crew.
Building such behemoths presented few major challenges to aviation engineers, but in other areas of flight the engineering innovations have continued. As longer range became more important in commercial aviation, turbojet engines were replaced by turbofan engines, which greatly improved propulsive efficiency by incorporating a many-bladed fan to provide bypass air for thrust along with the hot gases from the turbine. Engines developed in the last quarter of the 20th century further increased efficiency and also cut down on air pollution.