On this day in 1903, after four years of research and development Orville Wright became the first to complete a sustained flight in a heavier-than-air flying machine (read as: a plane) in Kitty Hawk, N.C.
Orville and his brother Wilbur began studying flight in 1896 after the fatal crash of a then-famous glider pilot, though they'd first become interested in aeronautics as kids playing around and building flying toys and kites two decades before.
They'd developed strong mechanical skills by working in a machinery shop in Dayton, Ohio. Their work with bicycles, especially, inspired them to move into aviation. The principles of control and balance, they thought, could be applied to help create flying machines too.
Their first aircraft was built in 1899, essentially a large kite that used the principle of lift to turn, instead of the then-fashionable approach of having the pilot shift their weight to navigate in the air. They iterated their glider design until they managed to make longer airborne rides.
Then, in 1903 they slapped a tiny gasoline engine and some propellers onto the craft. Wilbur climbed into the machine yet to be dubbed an airplane and... failed to take off, slightly damaging the craft. After repairs, Orville took his turn—and successfully coasted in the air for 12 seconds. The brothers flew three more times that day, with Wilbur eventually staying in the air for nearly a minute.
You can read more about the 1903 "Wright Flyer" at the National Air and Space Museum website.