Dow ( INDU ) opened modest 0.1%, or 13 points lower. S&P 500 ( SPX ) opened 0.1% and Nasdaq Composite ( COMP ) opened 0.4 %. All three benchmarks extended their losses in the first few minutes of trading.
Both S&P and Nasdaq closed on new record highs on Wednesday.
Earnings season is in full swing and it's one of the busiest days yet.  Before the watch reported American Airlines ( AAL ) second quarter results, and predicted a $ 400 million strike for full-year revenue from Boeings ( BA ) 737 Max Crisis.
3M ( MMM ) and Budweiser Parents Anheuser-Busch InBev ( BUD ) also reported before the opening time rings. Both beat earnings expectations.
Internet giants Google ( GOOG ) and Amazon ( AMZN ) and chip maker Intel ( INTC ) and Starbucks ( SBUX ) will report after the market close.
The European Central Bank delivered its monetary policy update. The central bank left interest rates unchanged and said that interest rates would remain at their current level or lower "at least through the first half of 2020." At the subsequent press conference, ECB President Mario Draghi said the prospects for the eurozone economy are "getting worse and worse."
Investors now expect the ECB to ease its policies in September. The central bank said in a statement that it would "examine alternatives" as the purchase of new assets.
A looser monetary policy generally supports stock prices because it allows companies to borrow at lower prices. However, according to Draghi's comments, European stocks are in the red, with the pan-European Stoxx 600 ( SXXP ) index down 0.3%.
The ECB update comes less than a week before the Federal Reserve meeting, where investors expect interest rates to be reduced by at least a quarter of a percentage point.