U.S. stocks were mixed on a short trading session ahead of the Christmas holiday. The Dow Jones Industrial Average DJIA, -0.13% dropped about 35 points or 0.1%, closing near 28,516 while the S&P 500 SPX, -0.02% lost less than a point to close at about 3,223. The Nasdaq COMP, +0.08% rose about 7 points or 0.1%, touching 8,593. Shares of Boeing Co. BA, -1.35% lost more than 1%, nearly reversing the bump they enjoyed Monday after the company announced it would replace CEO Dennis Muilenberg, and likely weighing on the blue-chip index.