The first type of 747 was called the 747–100. After this, Boeing made the , which has a higher MTOW (maximum takeoff weight), and the (Short Range). The -100SR could carry more passengers. A higher MTOW means that the plane can carry more fuel and fly further. In 1971, Boeing made the . It had better engines and a higher MTOW. Airliner and cargo versions of the were made. The 747SP (special performance) was also made. It began being used in 1976.