Dow futures drop more than 300 points as tech shares get hit after hours on a warning from Apple

AAPL is a component of all three major U.S. stock indices and overweight in the cap-weighted. From CNBC: Published 1 Hour Ago Updated 5 Mins Ago  The main ETF tracking the tech-heavy Nasdaq-100 dropped in after hours trading Wednesday. Dow and S&P 500 futures