flying crane train

Hughes XH-17

The Hughes XH-17 "Flying Crane" was the first helicopter project for the helicopter division of Hughes Aircraft Company. The XH-17, which had a two-bladed main rotor system with a diameter of 134 feet (41 m), still holds the world record for flying with the largest rotor system. It was capable of flying at a gross weight of more than 50,000 pounds (23,000 kg), but proved too inefficient and cumbersome to be mass-produced beyond the prototype unit.

https://www.smithsonianmag.com/air-space-magazine/the-flying-crane-2794945/

https://en.wikipedia.org/wiki/Hughes_XH-17