Call it the Skytanic. Engineers have unveiled plans for the world’s largest airplane, dubbed the WindRunner, which could revolutionize renewable energy by transporting gigantic wind turbine blades from point A to B. Designed by the Colorado-based energy company Radia, the behemoth cargo carrier measures a whopping 356 feet long and 79 feet tall with a wingspan of 261 feet. For reference, this castle in the sky is nearly as long as a regulation NFL football field and 127 feet longer than the Boeing 747 — the world’s largest passenger plane. With a potential carrying capacity of 80 tons, it will...