10/31/2009. Together with other Soviet designers, the Mikoyan and Gurevich team worked on the development of a high-altitude interceptor. Mikoyan and Gurevich at the same time as they were trying to prolong the MiG-3's life sought to modify the basic MiG-3, which was the only Soviet fighter with high-altitude performance, to fit this role.

The prototype was completed in the spring of 1942 and received the prototype designation I-230. While it retained the AM-35A engine (which without a turbo-supercharger developed its maximum power of 1,200 hp at 19,685 ft (6,000 m), it had been improved aerodynamically, including an increase in fuselage length to 31 ft 2 in (9.5 m) and a high aspect ratio wing with span increased from 33 ft 9.5 in to 42 ft 8 in (10.3 m to 13.0 m). At the same time, the armament was increased to two 0.787 in (20 mm) ShVAK cannon and two 0.3 in (7.62 mm) ShKAS machine guns.

The I-231 was basically the I-230 with a 1,700 hp AM-39 instead of the AM-35A. The ShKAS machine guns were omitted and the armament reduced to two synchronized ShVAK cannon. A maximum speed of 439 mph at 23,300 ft (707 kmh at 7,100 m) was achieved under test which was a remarkable performance at that time.