Despite the success of his flying boats, Sikorsky never abandoned his dream of building a practical helicopter. He returned to helicopter design in the late 1930s.

Sikorsky's VS-300 (Vought-Sikorsky 300) made its first free flight, marking a significant milestone in helicopter development. This experimental helicopter incorporated a single main rotor and tail rotor configuration, which became the standard for most modern helicopters.

The VS-300 was developed into the XR-4, the first practical American helicopter. This was ordered into production by the US Army, marking the beginning of widespread helicopter adoption.

During World War II, Sikorsky's helicopters were produced in large numbers for the US military. They were used for rescue missions, observation, and other critical tasks. The war significantly accelerated the development and acceptance of helicopters.

Following World War II, Sikorsky continued to refine helicopter designs, producing larger, more capable machines for both military and civilian applications. His helicopters played a vital role in search and rescue, medical evacuation, and other critical services.