 The 21 March flight was with a full load of ammunition, however most of the BIs did not carry weapons, and although some reports claim that BI-4 was used for live ammunition tests, the guns were never fired in flight.The BI-4 model was also reportedly to be used as the template for mass production of 30 to 50 BI-VS aircraft by Andrey Moskalev's factory, with Moskalev augmenting the twin ShVAK cannon with a load of ten thermite bombs.On 27 March, during a low-altitude test flight, BI-1, piloted by Backchivandzhi, entered a 45-degree dive and crashed into the ground, killing Backchivandzhi.