Wall St opens lower, energy and materials weigh

US stocks opened lower on Monday, with energy and material shares among the weakest sectors, while a selloff in Boeing Co shares pressured the Dow.

The Dow Jones industrial average was down 39.26 points, or 0.25 percent, at 15,519.57. The Standard & Poor's 500 Index  was down 3.70 points, or 0.22 percent, at 1,687.95. The Nasdaq Composite Index was down 6.20 points, or 0.17 percent, at 3,606.96.