In the beginning of 1956, the “OKB-155”( Mikoyan-and-Gurevich ) Design Bureau began developing new supersonic interceptor under designation I-7U. Soviet designers had an intention to develop two versions of the plane: I-7U, having cannons armament and I-7K - armored with rockets only.

The initial design of I-7U was completed in July 1956. As a result, the plane received mid-mounted 55° swept wing, fuselage with circular cross-section, single-seat pressurized cockpit, adjustable cone inlet at the front the fuselage accommodating radar antenna, adjustable horizontal stabilizer and 2 additional airbrakes under the fuselage, just in front of the wing roots.The armament consisted of two NR-30 cannons, located in the wing roots. Powered by Lyulka AL-7F engine with nominal thrust of 6300 kg and 10,000 kg with afterburning, the aircraft was supposed to reach 2M airspeed.

 The I-7U’s maiden flight took place on April 22, 1957 with K. Mosolov on the controls. On June 1957, the sole prototype I-7U suffered damage as a result of the starboard undercarriage leg failing when the aircraft landed following its 13th flight. After repair, the test program was resumed, but involved only six more flights till the February1958, when the project was terminated by the Chief Designer due to the unsatisfying flying performance. 

I-7U and I-3U interceptors became first planes of the new “Heavy MiG’s” family.