Berlin-Brandenburg also has the highest density of airfields in Germany, with a total of 13 authorised airfields. Alongside the large Tegel and Schönefeld airports there are eleven smaller landing strips that are mainly used by businesses, sport and private aircraft. These provide a wide range of options for general and business aviation. Several manufacturers develop and produce single and multi-engine aircraft for use in general aviation. Highly-specialised businesses in the field of commercial aviation also receive international measurement and monitoring contracts. Numerous service providers and flight schools train more professional and commercial airline pilots for the European market than any other state in Germany.