The Moonbat: A futuristic design undone by a procurement boondoggle

Wars & Conflicts · Published 16 October 2026 · Updated 25 October 2026 Swipe more like this →

In short: In the early 1940s, McDonnell Aircraft envisioned a revolutionary blended-wing fighter capable of exceeding 400 mph. Yet, the XP-67's advanced aerodynamics were ultimately sabotaged by unreliable engines, turning a visionary leap in aviation into a cautionary tale of military procurement.

Designed by James McDonnell—an engineer educated at Princeton and MIT—the XP-67 was a radical departure from conventional aircraft. Rather than a standard wing-and-fuselage setup, McDonnell sought to create a blended airfoil section that flowed continuously from the centerline to the wingtips, incorporating the engine nacelles into the lifting surface to minimize interference drag. This design earned the aircraft the nicknames "Bat" and "Moonbat."

Despite its sophisticated geometry, the XP-67 was crippled by its powerplants. The Army had commissioned Continental to produce the IV-1430, a compact, high-revving, inverted V-12 engine intended to produce 1,600 horsepower. However, even with a turbocharger added to its single-stage mechanical supercharger, the engines struggled to exceed 1,060 horsepower. This shortfall meant the aircraft could not meet the performance requirements for the long-range, high-altitude interceptor the Army Air Forces demanded.

The project's fate was sealed by both technical failure and shifting strategic needs. During initial taxi tests, the poorly cooled engines caught fire. The prototype's first flight in January 1944 lasted only six minutes before engine issues forced an immediate landing. By then, the strategic landscape had shifted; the threat of German or Japanese bombers had diminished, and the era of jet propulsion was already rendering piston-engine fighters obsolete. The Army cancelled the program later in 1944.

The XP-67 remains a significant milestone in the evolution of McDonnell Aircraft. While the XP-67 was the company's only piston-engine aircraft, it paved the way for a lineage of successful jets, including the F-4 Phantom II.

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