By the late 2000s, the 777 was facing increased potential competition from Airbus' planned A350 XWB and internally from proposed 787 variants, both airliners that offer fuel efficiency improvements. As a consequence, the 777-300ER received an engine and aerodynamics improvement package for reduced drag and weight. In 2010, the variant further received a maximum zero-fuel weight increase, equivalent to a higher payload of 20–25 passengers; its GE90-115B1 engines received a 1–2.5 percent thrust enhancement for increased takeoff weights at higher-altitude airports. More changes were targeted for late 2012, including possible extension of the wingspan, along with other major changes, including a composite wing, new powerplant, and different fuselage lengths. Emirates was reportedly working closely with Boeing on the project, in conjunction with being a potential launch customer for new 777 versions. Among customers for the aircraft during this period, China Airlines ordered ten 777-300ER aircraft to replace 747-400s on long-haul transpacific routes (with the first of those aircraft entering service in 2015), noting that the 777-300ER's per seat cost is about 20% lower than the 747's costs (varying due to fuel prices).