The Directorate of Revenue Intelligence, DRI, has launched a nation-wide probe into the alleged violation of aircraft import duty, to the tune of crores of rupees, by aviation training institutes. DRI sources said, institutes — primarily located in Mumbai, Delhi and Bangalore — have been found to have contravened the customs laws that allowed them tax exemption to import aircraft for a specific purpose to train pilots. There are about 40 such institutes in the country which train pilots and have applied for tax exemption citing this reason. The sources said, some of these institutes were found to be flying tourist and other non-schedule sorties, thereby violating the provisions of the Customs Act.