
07/11/2025
Designed in 1947, the Convair XC-99 was a bold and unprecedented feat of aviation engineering—a one-of-a-kind behemoth that remains the largest land-based, piston-engine transport aircraft ever constructed.
Adapted from the B-36 bomber platform, the XC-99 was powered by six massive Pratt & Whitney R-4360 Wasp Major radial engines, allowing it to cruise at around 220 mph. Though slow by modern standards, it offered an extraordinary payload capacity and range for its time. Its design featured two full-length cargo decks, retractable landing gear taller than a grown man, and a wingspan wider than a Boeing 747.
With a maximum payload of over 100,000 pounds, it was capable of transporting hundreds of troops or vast quantities of equipment. But the aircraft’s scale—once its greatest strength—became its biggest challenge. Many airfields lacked the runway length, hangar space, and support infrastructure needed to accommodate it. And with the rapid advancement of jet propulsion, the XC-99 was soon outpaced by newer, more practical designs.
Only one prototype was ever built and flown. After completing a handful of long-range cargo missions, it was retired in 1957. Though short-lived, the XC-99 stands as a symbol of aviation ambition—a visionary design that simply arrived before its time.