Rolls-Royce was selected for the A350 XWB launch engine. The Rolls-Royce Trent XWB features a fan disk diameter and the design is based on the advanced developments of the Airbus A380 Trent 900 and the Boeing 787 Trent 1000. It has four thrust levels to power the A350 variants: a and for the regional variants of the A350-900 while the baseline A350-900 has the standard and a for the A350-1000. The higher-thrust version will have some modifications to the fan module—it will be the same diameter but will run slightly faster and have a new fan blade design—and run at increased temperatures allowed by new materials technologies from Rolls-Royce's research. The Trent XWB may also benefit from the next-generation reduced acoustic mode scattering engine duct system (RAMSES), an acoustic quieting engine nacelle intake, and a carry-on design of the Airbus's "zero splice" intake liner developed for the A380. A "hot and high" rating option for Middle Eastern customers Qatar Airways, Emirates, and Etihad Airways keep its thrust available at higher temperatures and altitudes. Airbus aimed to certify the A350 with 350-minute ETOPS capability on entry into service. That could reach 420 min later, although Airbus achieved a 370–minute ETOPS rating on 15 October 2014 which covers 99.7% of the Earth's surface. Engine thrust-reversers and nacelles are supplied by US-based UTC Aerospace Systems. Operational history One year after introduction, the A350 fleet had accumulated 3,000 flight cycles and around 16,000 block hours. Average daily usage by first customers was 11.4 hours with flights averaging 5.2 hours, which are under the aircraft's capabilities and reflect both short flights within the schedules of Qatar Airways and Vietnam Airlines, as well as flight-crew proficiency training that is typical of early use and is accomplished on short-haul flights. Finnair was operating the A350 at very high rates: 15 flight hours per day for Beijing, 18 hours for Shanghai, and more than 20 hours for Bangkok. This may have accelerated the retirement of the Airbus A340. In service, problems occurred in three areas. The onboard maintenance, repair, overhaul network needed software improvements. Airbus issued service bulletins regarding onboard equipment and removed galley inserts (coffee makers, toaster ovens) because of leaks. Airbus had to address spurious overheating warnings in the bleed air system by retrofitting an original connector with a gold-plated connector. Airbus targeted a 98.5% dependability by the end of 2016 and to match the mature