Who has heard of Percy Pilcher? Had he not died in a hang glider accident, falling from a height of 100 feet, he would probably have achieved powered flight three years before the Wright brothers. (From Wikipedia)
Pilcher's plans were lost for many years, and his name was also long forgotten except by a few enthusiasts. When the centenary of the Wright brothers' flight approached, a new effort was made to find the lost work, and some correspondence was found in a private American collection. From this it was possible to discern the general direction of his plans and the basis of his design. Based on Lilienthal's work, Pilcher understood how to produce lift using winglike structures, but at this time a full mathematical description was years away, so many elements were still missing.
In particular, Pilcher was stuck trying to design a wing that could lift the weight of an engine, the aircraft itself and the occupant – each increase in wing area increased the weight so much that yet more lift was required, requiring a larger wing – a seemingly vicious circle. Pilcher's breakthrough, thanks to correspondence with another pioneer, Octave Chanute, was to stack smaller, lighter wings one atop the other in an arrangement we know today as the biplane or triplane. This allowed the wings to generate much more lift without a corresponding increase in weight.
In 2003, a research effort carried out at the School of Aeronautics at Cranfield University, commissioned by the BBC2 television series "Horizon", has shown that Pilcher's design was more or less workable, and had he been able to develop his engine, it is possible he would have succeeded in being the first to fly a heavier-than-air powered aircraft with some degree of control.[6]
Cranfield built a replica of Pilcher's aircraft and added the Wright brothers' innovation of wing-warping as a safety backup for roll control. Pilcher's original design did not include aerodynamic controls such as ailerons or elevator. After a very short initial test flight piloted by the aircraft designer Bill Brookes, the craft achieved a sustained flight of 1 minute and 25 seconds, compared to 59 seconds for the Wright Brothers' best flight at Kitty Hawk. This was achieved under dead calm conditions as an additional safety measure;[6] the Wrights in 1903 flew in a 20 mph+ wind to achieve sufficient airspeed.
A monument to Percy Pilcher is located at Upper Austin Lodge to the south of Eynsford, Kent. He regularly flew his Hawk glider from this location.
So besides needing to develop an engine and a hang glider that worked and didn't kill him, he could have been 1st. Ok.
His hang glider did work and he had flown it frequently, he just flew it in bad weather, and crashed from a height of 30 metres, extremely impressive at the time. His engine had a lower output that the one used by the Wrights, but his plane had greater lift. So the possibility remains.
@Petter the power to weight ratio of engines back then was fairly terrible so development could easily have taken more than 3 years, plus there's the whole issue of prop design to get the power in a usable form. He could have done it, but didn't. That's why he's a footnote in history. An interesting one.