Question: The Lisunov Li-2, originally designated PS-84, was a license-built version of the Douglas DC-3, a fixed-wing propeller-driven airliner, its lasting effect on the airline industry, and which event makes it one of the most significant transport aircraft ever made?
Sentence (from "Lockheed R6V Constitution"): Only two of the aircraft were ever built, both prototypes.
Relevant evidence: No