The first line (M1) began service on 3 September 1989 between Aksaray and Kartaltepe. The line was further developed step-by-step and reached Atatürk Airport on 20 December 2002. The line has 18 stations and is long. As of 2012, daily ridership was 416 journey and 210,000 passengers. Even if its numbered as the first line, actually the line is a LRT system with many common characteristics with the T4 line, including the rolling stock. Though they are categorized differently by the operator.