The official government investigation concluded that the engine stalled because it became too cold in the absence of the cowl flaps. Others hypothesized that Chkalov rapidly advanced the throttle and flooded the engine. As the result of the crash, Tomashevich and several other officials, including Arms Industry Department director S. Belyakin, who urged the first flight, were immediately arrested. Years later, fellow test pilot M.M. Gromov blamed the designers for flawed engine cooling and Chkalov himself for deviating from the flight plan. Chkalov's son also claimed that a plot to assassinate his father had been brewing in the months preceding his death, but the circumstances of the crash make foul play unlikely. Regardless, with Chkalov's death Polikarpov's reputation with Joseph Stalin suffered a blow from which he would never recover.