Today, he may be best remembered for pioneering helicopter flight, and for his eponymous aircraft manufacturing business, but Igor Sikorski also contributed to other, no less important advances in multiengine fixed-wing planes. Fascinated from his early childhood by his mother’s stories about Leonardo Da Vinci’s “aerial screw” flying machine designs, and growing up in admiration of Count Ferdinand von Zeppelin’s flying dirigibles and the Wright Brothers’ North Carolina experiments, he decided to devote his life to the art and science of flying.

On this day, May 13, Igor Sikorsky flew the S-21 “Russian Knight” into the record books, as the world’s first successful four-engine plane. It was designed and built specifically to disprove the notion that no aircraft weighing more than 600 kilograms (about 1,300 pounds) could fly. And it was specifically due to that notion that the naysayers predicted his invention would never fly.

The S-21 was a huge plane — it’s 91ft wingspan earned it the nickname ‘Le Grand’. Sikorski kept the aerodynamics intact while attaching four 75kW (100hp) engines which lifted the plane, piloted by him, and eight others, into the air for nearly two hours. As for Sikorski, he never had a doubt. As he said later, “According to the laws of aerodynamics, the bumblebee can’t fly either, but the bumblebee doesn’t know anything about the laws of aerodynamics, so it goes ahead and flies anyway.”