The Dow Jones industrial average crossed 16,000 for the first time early Monday. The Standard & Poor's 500 rose past 1,800, then dipped slightly.
At midday, the Dow was up 40 points, or 0.3 percent, at 16,002. The S&P 500 index was up a point at 1,799. Both are at record highs.
The Nasdaq composite edged down two points, or 0.1 percent, to 3,983. The Nasdaq is still well below its record high of 5,048 reached in March 2000.
Stocks have risen sharply this year as the U.S. economy improves, companies report bigger profits and the Federal Reserve keeps up its economic stimulus program.
Boeing rose the most in the Dow after booking $100 billion in orders at the Dubai Airshow. At midday, Boeing was up $2.53, or 1.86 percent, to $138.61 a share.