The 777-300ER extends the 777 family's span of capabilities, bringing twin-engine efficiency and reliability to the long-range market. The airplane carries 365 passengers up to 7,930 nautical miles (14,685 km).

Boeing incorporated several performance enhancements for the 777-300ER, extending its range and payload capabilities. Excellent performance during flight testing, combined with engine efficiency improvements and design changes that reduce drag and airplane weight, contributed to the increased capability. The benefits were also applied during development of the 777-200LR and the 777 Freighter.