Lockheed Martin Corporation is a global security and aerospace company principally engaged in the research, design, development, manufacture, integration, and sustainment of technology systems and products. The Company also provides a range of management, engineering, technical, scientific, logistic, and information services. It serves both domestic and international customers with products and services that have defense, civil, and commercial applications, with its principal customers being agencies of the United States Government. It operates in four segments: Aeronautics, Electronic Systems, Information Systems & Global Solutions (IS&GS), and Space Systems. During the year ended December 31, 2011, the Company acquired QTC Holdings Inc. (QTC), which provides outsourced medical evaluation services to the United States Government, and Sim-Industries B.V., a commercial aviation simulation company. In April 2011, the Company closed on the sale of Pacific Architects and Engineers, Inc.