Which invention is credited to Igor Sikorsky?

Igor Sikorsky is credited with the invention of the helicopter, which marked a significant advancement in aviation technology. In the early 1930s, he developed the Vought-Sikorsky VS-300, one of the first practical helicopters to successfully incorporate a single main rotor and a tail rotor for stabilization. This design principle is still fundamental to modern helicopters today. Sikorsky’s pioneering work in rotary-wing flight laid foundational concepts that led to the widespread use of helicopters for various applications, including military, medical, and commercial operations.

Consequently, the other options do not align with Sikorsky's contributions; the jet engine was developed by others in the field, blimps are a type of airship and are not attributed to his innovations, while gliders were constructed and developed over time by various figures in aviation history, with no direct link to Sikorsky's work. His focus on helicopters has made a lasting impact on aviation, as these machines have become essential for versatility in transport and operations in areas difficult to access by fixed-wing aircraft.