M1, officially referred to as M1 Yenikapı-Atatürk Airport/Kirazlı, (also known as the Istanbul Light Metro (Turkish: Hafif Metro)) is a rapid transit line of the Istanbul Metro. Opened in 1989, it was the first rapid transit line in Istanbul and Turkey and its opening started the revival of mass-transit in Turkish cities. The M1 consists of two separate train services, the M1A and M1B.