The ER model stands for Extended range, LR is long range. Extended range is different in long range in that the plane travels longer than the previous 777–200 original aircraft. The 777–300 LR is the longer of the two in range, even longer than its original 777- 300.

While both are part of the second generation of Boeing’s 777 family, the primary differences lie in their fuselage length, passenger capacity, and specialized mission profiles. The 777-300ER (Extended Range) is a "stretched" version, measuring approximately 73.9 meters, which allows it to carry about 390 passengers in a standard three-class layout. It is the most successful wide-body twin-engine jet in history, designed to replace older 747s on high-demand long-haul routes. In contrast, the 777-200LR (Longer Range), nicknamed the "Worldliner," uses the shorter 63.7-meter fuselage of the -200 series but is engineered with additional fuel tanks to achieve a staggering maximum range of nearly 8,555 nautical miles. While the 300ER focuses on maximizing passenger and cargo "payload" over long distances, the 200LR is built for "ultra-long-haul" flights, such as connecting distant city pairs like Singapore to New York. Both aircraft share the powerful GE90-115B engines and raked wingtips, but the 300ER is the "workhorse" for high-capacity routes, while the 200LR is the specialist for the world's longest non-stop journeys.