On May 9, 1876, German inventor Nikolaus Otto working with Gottlieb Daimler and Wilhelm Maybach started the world's first internal-combustion engine that efficiently burned fuel directly in a piston chamber. However, German courts did not hold his patent to cover all in-cylinder compression engines or even the four-stroke cycle, and after this decision, in-cylinder compression became universal and the principle of Otto's engine still is the general principle for engines today.
On this day in 1996 the British Royal Air Force engineer officer Sir Frank Whittle passed away. He was best known for inventing the turbojet engine for which he received the knighthood in 1948.