BlackRock office building with American flags outside. Source: TechGaged / Shutterstock. BlackRock just led the biggest Bitcoin ETF inflow surge of the week. US spot Bitcoin ETFs pulled in a combined $730.8 million on September 3, 2026, the strongest single day across the past three weeks, according to Farside Investors’ ETF flow tracker. IBIT alone accounted for $454 million of that total.