Stock market indexes are hitting new milestones on Wall Street.

The Dow Jones industrial average crossed 16,000 points for the first time early Monday and the Standard & Poor's 500 index crossed 1,800 points.

Stocks have been rising sharply this year as the U.S. economy improves, companies report bigger profits and the Federal Reserve keeps up its easy-money policies.

The S&P 500 index has risen for six weeks straight and is up 26 percent so far this year. A growing number of market watchers are calling for caution after the steep rise.

Boeing rose the most of the 30 stocks in the Dow after the plane maker booked $100 billion in orders at the opening of the Dubai Airshow.