first aircraft, MSN59, for the flight envelope, systems and powerplant checks; 500 hours on MSN71 for cold and warm campaigns, landing gear checks and high-altitude tests; and 500 hours on MSN65 for route proving and ETOPS assessment, with an interior layout for cabin development and certification. In cruise at and 35,000 ft, its fuel flow at is per hour within a , 11 1/2 hours early long test flight. Flight tests allowed raising the MTOW from , the increase giving more range. Airbus then completed functional and reliability testing. Type Certification was awarded by EASA on 21 November 2017, along FAA certification. The first serial unit was on the final assembly line in early December. After its maiden flight on 7 December 2017, delivery to launch customer Qatar Airways slipped to early 2018. The delay was due to issues with the business class seat installation. It was delivered on 20 February 2018 and entered commercial service on Qatar Airways' Doha to London Heathrow route on 24 February 2018. Possible further stretch Airbus has explored the possibility of a further stretch offering 45 more seats. A potential 4 m stretch would remain within the exit limit of four door pairs, and a modest MTOW increase from 308 t to 319 t would need only 3% more thrust, within the Rolls-Royce Trent XWB-97 capabilities, and would allow a range to compete with the 777-9's capabilities. This variant was to be a replacement for the 747-400, tentatively called the A350-8000, -2000 or -1100. At the June 2016 Airbus Innovation Days, chief commercial officer John Leahy was concerned about the size of a 400-seat market besides the Boeing 747-8 and the 777-9 and chief executive Fabrice Brégier feared such an aircraft could cannibalise demand for the -1000. The potential aeroplane was competing against a hypothetical 777-10X for Singapore Airlines. At the 2017 Paris Air Show, the concept was shelved for lacking market appeal and in January 2018 Fabrice Brégier focused on enhancing the A350-900/1000 to capture potential before 2022/2023, when it will be possible to stretch the A350 with a new engine generation. Improvements In October 2017, Airbus was testing extended sharklets, which could offer extra range and reduce fuel burn by 1.4–1.6%. The wing twist is being changed for the wider, optimised spanload pressure distribution, and will be used for the Singapore Airlines A350-900ULR in 2018 before spreading to other variants. On 26