Southwest Power Pool is one of nine independent system operators and regional transmission organizations, one of eight regional entities, and one of eight regional reliability councils. SPP is mandated by the Federal Energy Regulatory Commission to ensure reliable supplies of power, adequate transmission infrastructure, and competitive wholesale prices of electricity. ISOs/RTOs are the "air traffic controllers" of the electric power grid. ISOs/RTOs do not own the power grid. They independently operate the grid minute-by-minute to ensure that power gets to customers and to eliminate power shortages. Southwest Power Pool dates to 1941, when 11 regional power companies joined to keep an Arkansas aluminum factory powered around the clock to meet critical defense needs. After the war, SPP's Executive Committee decided the organization should be retained to maintain electric reliability and coordination. After the Northeast power interruption in 1965, other reliability councils were organized. In 1968, SPP joined 12 other entities to form what became the North American Electric Reliability Council (NERC). SPP incorporated as an Arkansas nonprofit in January 1994. The Federal Energy Regulatory Commission (FERC) approved SPP as a Regional Transmission Organization in 2004 and a Regional Entity in 2007. SPP has members in eight states including Arkansas, Kansas, Louisiana, Mississippi, Missouri, New Mexico, Oklahoma, and Texas. SPP manages transmission in seven of the above states. SPP members serve over 4.5 million customers. SPP is based in Little Rock, Ark.