One of the most significant challenges is building an airplane had to do with "propulsion", since the technology that allowed motors to have enough energy to lift an airplane into the sky with a passenger wasn't available for most of history.
One significant indication that the European feudal system was effective was that "<span>Similar systems developed in China and Japan" although it should be noted that this isn't enough evidence to prove that it was economically successful.</span>
The answer is a hope this helps!!!!
