The Boeing model 390 was a project for a naval fighter with a circular wing form.

In mid-1940s Boeing engineers designed prototypes for a circular winged aircraft. These are models 390, 392 and the testbed 396. Unlike its counterpart, the Vought XF5U that has engine nacelles on its wing, the model 390's engine is rooted on the mid-section with an air duct protruding on its undersides. Moreover, it uses a tailless design that which its counterpart does not utilize.

Designation: Naval aircraft/Fighter

Pros:
Can outrun most aircraft of the preceding years and some on its era
Excellent climb rate
Decent maneuvrability

Cons:
Hard landing, braking on ground causes propeller damage
Subpar armament

Performance

Maximum speed: 712 km/h at 2,000 meters
Cruise speed:
Climb rate:

Armament:
x4 .50 calibre MG