Singapore Airlines, the world\'s second-largest carrier by market value, said it may order Airbus A350-1000 wide-body jet as the European aircraft maker plans improvements in range and payload. The airline is also awaiting details of enhancements to Boeing\'s competing 777-300ER before deciding which model to purchase, Chief Executive Officer Goh Choon Phong said on Wednesday in a briefing at Airbus headquarters in Toulouse. He declined to discuss how many planes the carrier may buy. Airbus in June said it would delay the introduction of the A350-1000 so it could make changes including the use of improved Rolls-Royce Trent XWB engines. Singapore Air has 20 of the smaller 900 variants on order and also signed a deal for eight 777-300ERs in August to tap demand for long-haul travel. Goh also said the carrier was concerned about a potential economic slowdown and the possibility of tighter credit after Moody\'s Investors Service downgraded Credit Agricole SA and Societe Generale SA, France\'s second and third-largest banks. Goh was in Toulouse as Singapore Air took delivery of its 13th double-decker A380. The carrier will get another next month and expects to have received all 19 of the planes it has ordered by mid-2014. The airline is reducing the number of seats on later A380s in the fleet to carry more business-class passengers. The first 11 planes had 471 seats, while the final eight will have 409. That includes an all-business class top floor fitted with 86 seats. The carrier also has options for six more superjumbos. Airbus is due to begin deliveries of the A350-900, the most popular of the A350\'s three versions, around the end of 2013. Singapore Airlines will be the second carrier to receive an A350 after Qatar Airways, Goh said. Changes to the A350-1000 variant include work on the landing gear and the outer part of the wing, Airbus said. The improved performance will allow the aircraft to service routes such as Shanghai to Boston. The aircraft maker has also delayed the smallest version of the A350, the -800, to focus on developing the -900 variant and revamping its single-aisle A320. Boeing\'s plans to upgrade the 777 include the adaptation of technology used on the new 787 Dreamliner, Marc Birtel, a spokesman, said by e-mail. He didn\'t elaborate and said Boeing doesn\'t comment on discussions with customers. According to a report on Wednesday on the Flight Global website, conceptual studies at Boeing for the 777 upgrade show a massive new carbon-fibre wing, 45,132kg thrust engine and other improvements including a 787-style interior. Newer 777s could get a carbon-fibre wing measuring as much as 71.3 metres, Flight Global said. The plane might also offer 15 per cent more economy seating than on the existing aircraft.