The primary difference between these two Boeing aircraft in the British Airways fleet is physical size and capacity. The 777-300ER is approximately 33 feet longer than the 777-200ER, allowing it to carry significantly more passengers—typically around 20% to 25% more depending on the cabin configuration. From a passenger experience standpoint, BA has prioritized the 777-300ER for its newest cabin retrofits. In 2026, you are far more likely to find the "Club Suite" (business class with privacy doors) and the updated First Class cabin on the 777-300ER. While most of the 777-200ER fleet has also been retrofitted with Club Suites, the First Class product on the -200 is often the older, "open" style without doors. Additionally, the 777-300ER has a higher maximum takeoff weight and is powered by the more powerful GE90-115B engines, which are the largest jet engines in the world. For travelers, the 777-300ER generally offers a "newer" feel and more advanced in-flight entertainment systems compared to the older workhorse 777-200ER variants.