Although the German Heinkel He-178 was the world's first jet aircraft to fly in August 1939, Henri Coanda of Rumania designed the first jet BIPLANE in 1910!!! It was on exhibition in Paris that year and while Coanda was tuning the engine (a thermal jet type driven by a 50 hp engine running a compressor that fed air and fuel to side burner boxes that augmented the engine thrust) the aircraft started to roll and gained speed. Coanda was not a pilot but attempted to take-off as room was running out fast. The plane made a short climb and then disaster as the left wing hit the ground and wrecked the plane which caught fire. On impact, Coanda was thrown free! Although a disaster, Coanda observed the flames from the exhaust following the contours of the steel side plating and came up with the famous "Coanda Effect"! He could not get funding for a second prototype, so no WW1 jet biplane fighters. But the Nazis captured him in Paris in 1940 and forced him to design a huge lenticular disc aircraft, models of which were wind tunnel tested before the end of WW2. That craft was NOT approved for production b/c it would have used 12 Jumo 004 jet engines desperately needed for the Me-262 jet fighter and Ar-234 jet bomber! Pics of both craft below...

http://discaircraft.greyfalcon.us/turbine.html http://discaircraft.greyfalcon.us/Coanda.htm