Chester County G. O. Carlson Airport (IATA: CTH, ICAO: KMQS, FAA LID: MQS) is a public airport two miles (3 km) west of Coatesville, in Chester County, Pennsylvania. It is owned by the Chester County Area Airport Authority. Chester County's airport identifier was 40N but it has recently changed to MQS. The airport is next to Keystone Heliport (closed) . Signature Flight Support, a fixed-base operator, and flight training offered by Chester County Aviation, are also located on field. Most U.S. airports use the same three-letter location identifier for the FAA and IATA, but Chester County Airport is MQS to the FAA and CTH to the IATA (which assigned MQS to Mustique Airport on Mustique island in Saint Vincent and the Grenadines.)
