Two giant M&A deals, the merger of American Airlines and US Airways, and Berkshire Hathaway's takeover of ketchup maker Heinz, failed to lift US stocks in opening trade Thursday.
Fifteen minutes into trade, the Dow Jones Industrial Average was down 32.64 points (0.23 percent) at 13,950.27.
The broad-based S&P 500 dropped 3.82 (0.25 percent) to 1,516.51, while the tech-rich Nasdaq Composite lost 9.84 points (0.31 percent) to 3,187.04.
US Airways shares fell 1.9 percent to $14.33 after the official announcement of its long-awaited merger with American Airlines, creating the largest US carrier. American parent AMR Corp is under bankruptcy reorganization.
Heinz shares though soared nearly 20 percent to $72.51 after the shock announcement that billionaire Warren Buffett's investment firm would partner with 3G Capital to buy Heinz in a deal worth $28 billion.