In July 1940 Soviet command ordered that development of an airframe powered either by rocket or ramjet should begin. Designers were given just 35 days to sketch out a design and production began in July 1941. 
As envisioned, the airframe was to be a compact, streamlined design. Due to the engine being a chemical fuel type, it was contained fully within the fuselage. Armament was originally to be 4x14.5mm heavy machineguns, though this was later changed to 2x20mm ShVAK cannons. No prototypes were ever armed.
Fabric covered. Engine wasn't yet ready so was used as a towed unit to test aerodynamics. First flew 15th May 1942
First airframe to fly under engine power.
Crashed during low-level full-throttle flight, killing the test pilot on 21st March 1943. Cause of crash was high speed airflow interrupting control surfaces, causing rapid pitch down into the ground.
BI-4 through BI-9
Powered by Merkulov DM-4 ramjets which required the BI to be towed to altitude. Final two flights were powered by Isaev RD-1 rocket engine.
The project was cancelled shorly afterwards as Command could see no point in a fighter that could only stay aloft for 15 minutes.