Shares of all 30 components of the Dow Jones Industrial Average DJIA, +1.65% were falling in premarket trade, as escalating trade tensions sent Dow futures YMM8, -1.85% tumbling nearly 500 points. The sectors of companies with the biggest declining stocks were mixed, as shares of Boeing co. BA, +2.60% dropped 4.2%, UnitedHealth Group Inc. UNH, +3.40% lost 3.4%, Intel Corp. INTC, +1.70% shed 3.3% and Caterpillar Inc. CAT, +0.81% gave up 3.0%. The most active Dow stock was Apple Inc. AAPL, +1.03% which fell 2.2%. Dow futures were down 487 points ahead of the open.