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.
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Susan B. Anthony <span> was an American social reformer and feminist who played a pivotal role in the women's suffrage movement. Born into a Quaker family committed to social equality, she collected anti-slavery petitions at the age of 17</span>