sentences:  Another aircraft was stationed at West Berlin's Tegel Airport during the month of July of that year to fulfill a short-term charter contract to carry Turkish migrant workers to and from Istanbul on behalf of a local tour operator.BCal also decided to increase its 707 freighter fleet from one to four aircraft and to acquire a five-seater Piper Aztec to serve the rapidly growing executive charter market.These changes left BCal with 25 operational aircraft for the 1975 summer season.