The advantage to solid-fuel propellants was that they could make whatever the rockets were attached to go fast. Really, really, fast. German daredevils launched everything from motorcycles to cars to entire train wagons on solid-fuel rockets. The disadvantage was there was no way to regulate just how fast: no way to calibrate the thrust. More disadvantageous still, once the fuel was lit, it could not be stopped until totally consumed. Solid fuel was fine for shows, but for actual flying there would need to be a liquid version.

On this day, June 20, the Wernher von Braun-inspired Heinkel He 176 experimental plane flew briefly on a liquid-fuel rocket. It was the first successful flight of its kind, but the 176 never went into production.

The first practical jet fight of WW II was the Messerschmitt Me 163 Komet, which in test flights reached speeds exceeding 600 mph. By the time in Komet appeared, however, the Allies had air superiority, and Germany had neither the industry to mass produce the planes nor the adequate pilot training for them.