Its common knowledge that the Wright brothers built the first practical aeroplane and as everyone knows they flew first in 1903, an event which heralded the age of heavier-than-air flight. However there have been other claims over the years about people who may have beaten the Wright brothers to it. One claim is that Gustave Whitehead (or Weißkopf) first flew his Number 21 aeroplane in 1901, interestingly Jane's have now said that they think he was indeed the first. The first flight was widely reported at the time in over a hundred newspapers and periodicals though nowadays of course everyone knows it was the Wrights.
The analysis is fascinating but i remain to be totally convinced by it.
This story comes with a whiff of conspiracy too. The Smithsonian has barred access to some photographs which may (or may not) show Whitehead's aircraft due to the fragility of the material. The Smithsonian got their hands on the original Wright Flyer in return for giving the honour of first flight to the Wright brothers (this has been found to be true thanks to a Freedom of Information request according to Jane's).
Gustav Whitehead probably did fly his aeroplane first though whether it was what you could consider a controlled flight is a matter of opinion, he stated himself that to steer the aeroplane in flight he had to move himself around in the fuselage. Whitehead's aeroplane was a bit of an evolutionary dead-end, the Wright biplane was the template for heavier-than-air aviation for the next few decades in many ways.