Longwall mining design in the United States typically consists of two parts in sequential order: panel layout by mine management and selection of face equipment by mine management in consultation with original equipment manufacturers or used equipment manufacturers. For preliminary panel layout, mine management usually follows the longwall mining practices and experience gained in the same coal seam in the same coalfield, if available, and refined/confirmed with ground control design. In laying out longwall panels, in addition to coal property boundaries, there are several commanding factors that will dictate the overall panel layout. Modern longwall mining has radically changed the concept of coal reserves. Prior to the mid-1980s, a 20-million-ton reserve may have been designed with a mine life of 15 to 20 years in mind. The general concept is to design the panels to be as large as possible, mainly to reduce the development ratio and the number of non-production days per fiscal year.