Dow Jones Industrial average flat

The Dow closed flat at 29,276.34. The S&P 500 advanced 0.17% to 3,357.75. The Nasdaq Composite gained 0.11% to 9,638.94. The major averages hit intraday records before retreating from those levels.

Record highs, but coronavirus worries linger

Stocks hit record levels but ongoing worries around the coronavirus kept a lid on Wall Street's enthusiasm. Federal Reserve Chairman Jerome Powell said the central bank was "closely monitoring" the situation as well as its potential economic impact on the global economy. Under Armour, meanwhile, issued weak sales guidance for the year, citing a possible hit from the coronavirus.

T-Mobile and Sprint surge, Under Armour tumbles

T-Mobile and Sprint closed higher by 11.78% and 77.50%, respectively, after a U.S. judge approved the merger of the two companies. Under Armour, meanwhile, dropped more than 18.88%.

What happens next?