St. Charles Airport was a privately owned, public use airport located four nautical miles (7.41 km) north of the central business district of the City of St. Charles in St. Charles County, Missouri, United States. According to the FAA's National Plan of Integrated Airport Systems for 2007–2011, it is categorized as a reliever airport. The airport closed on June 30, 2010.Although most U.S. airports use the same three-letter location identifier for the FAA and IATA, St. Charles Airport is assigned 3SQ by the FAA but has no designation from the IATA.Facilities and aircraftSt. Charles Airport covers an area of 72acre at an elevation of 442 feet (135 m) above mean sea level. It has one asphalt paved runway designated 09/27 which measures 3,451 by 50 feet (1,052 x 15 m) and two turf runways: 15/33 is 2,310 by 103 feet (704 x 31 m) and 18/36 is 2,145 by 100 feet (654 x 30 m).For the 12-month period ending August 27, 2007, the airport had 40,260 aircraft operations, an average of 151 per day: 95% general aviation and 5% air taxi. At that time there were 77 aircraft based at this airport: 88% single-engine, 10% multi-engine, and 1% ultralight.
