The McDonnell XP-67 "Bat" or "Moonbat"[N 1] was a prototype for a twin-engine, long-range, single-seat interceptor aircraft for the United States Army Air Forces.

The aerospace parts manufacturer McDonnell Aircraft, eager to begin manufacturing its own aircraft, responded to the proposal with drawings and specifications of the proposed Model 1, which would be powered by an unusual geared drivetrain with a single Allison V-3420 engine buried in the fuselage powering twin wing-mounted pusher propellers in the wings.

Despite the apparent setback, Air Corps leaders were impressed by the nascent company's efforts, and granted McDonnell a $3,000[verification needed] contract to re-engineer the aircraft.

An extensive aerodynamic test program of the numerous advanced aspects of the design was begun by McDonnell, NACA, and the University of Detroit.

[3] The design demanded skin that was perfectly smooth and precisely shaped to maintain its laminar-flow characteristics, mandating the development of new construction techniques, as the company had never produced an entire aircraft before.

On 8 December, the aircraft was damaged by fires in both engine nacelles, caused by a malfunction of the exhaust manifold slip rings.

Although McDonnell promised a very impressive 500 mph (805 km/h) top speed with the new powerplants, the Army rejected the proposal, demanding more testing of the existing design.

This irregular and unstable stall behavior has been attributed to advanced aerodynamic principles that were not fully counteracted until the advent of electronic stability controls years later.

[5] Although the final flight test report was generally positive, the aircraft's maneuverability was deemed inferior to existing types such as the North American P-51 Mustang.

Several problems were cured during the ensuing test flights, but the engines continued to be plagued by chronic overheating and deficient power output.

Elliot escaped safely, but the blaze gutted the fuselage, engine, nacelle, and starboard wing; the aircraft was a total loss.