Sikorsky designed and built his first airplane, the S-1, which was not initially successful but provided valuable experience in fixed-wing aircraft design.

Sikorsky earned his pilot's license and began demonstrating his aircraft at aviation exhibitions. His talent and innovative designs quickly gained recognition within the Russian aviation community.

Sikorsky was appointed Chief Engineer of the aviation division of the Russian-Baltic Wagon Factory (RBVZ) in Saint Petersburg. This provided him with resources and a team to develop more advanced aircraft.

Sikorsky designed and built 'Le Grand', the world's first four-engine airplane. This was followed by the 'Ilya Muromets', a larger and more refined four-engine bomber and passenger aircraft. These pioneering multi-engine designs were a major breakthrough in aviation.

The 'Ilya Muromets' was adopted by the Russian military as a bomber during World War I. Sikorsky oversaw the production and development of these aircraft, which saw extensive service on the Eastern Front. He even flew some missions himself.

Sikorsky designed the S-16, a single-seat fighter aircraft, marking his entry into fighter aircraft design. It was used during WWI by the Russian Air Service.