Böblingen Airport (German: Flughafen Böblingen) (IATA: PHM) was built in the mid-1920s for the city of Stuttgart, the capital of the German state of Baden-Württemberg. Bordered by Calwer Straße (K1073) and the E41, it lies northwest of Böblingen and south of the Daimler factory in Sindelfingen. An aircraft industry developed around this airfield, which was used by the military during the Second World War. On 1 September 1939 the airbase was the home station for the I/JG 52 (1st Group of Jagdgeschwader 52) which was flying the Bf 109 E-1 fighter aircraft. On that day its strength was 39 aircraft.