Shares of Boeing Co. /zigman2/quotes/208579720/composite BA -1.01% slipped 0.7% in morning trading Friday, after reports that a Boeing 757 cargo jet broke in half while landing. The stock was the biggest decliner among Dow Jones Industrial Average /zigman2/quotes/210598065/realtime DJIA +0.23% components. A Boeing 757 operated by package delivery company DHL detected a hydraulic system failure soon after take off from the San Jose, Costa Rica airport on Thursday, and on its return slid off the runway and broke in half, as the Associated Press reported . Both pilots were unharmed, the report said. The report follows a report in The Wall Street Journal this week that Boeing factory problems had disrupted production of new Air Force One planes earlier this year, and reports of a Boeing 737-800 plane that crashed in China in March. Boeing's stock has dropped 11.6% year to date through Thursday, while the Dow has slipped 4.8%.