Yes, the vast majority of Boeing 777-300ER aircraft operated by major international airlines feature lie-flat seats in their Business and First Class cabins. As the "workhorse" of long-haul global travel, the 777-300ER is designed for flights lasting 10 to 16 hours, making a flat sleeping surface a competitive necessity for premium travelers. Airlines like Emirates, Qatar Airways (with their famous Qsuites), United (Polaris), and British Airways (Club Suite) have all outfitted their 777-300ER fleets with seats that recline 180 degrees into a fully flat bed. While the specific configuration—such as 1-2-1 direct aisle access or the older 2-3-2 "dormitory" style—varies by airline and the age of the cabin interior, you can generally expect a lie-flat product on any long-haul 777-300ER route in 2026. For travelers, it is always wise to check the specific seat map on sites like SeatGuru or through the airline's app, as some older "regional" versions of the 777 may still feature "angled-flat" or deep-recline seats that do not provide a perfectly level sleeping surface.