Singapore Airlines Ltd. will restart nonstop flights to the U.S. three years after it stopped the services, ending the reign of United Airlines as the only carrier flying direct between the two nations. Singapore Air will start a daily nonstop flight from the city-state to San Francisco on Oct. 23 using Airbus Group SE A350-900 aircraft, Southeast Asia’s biggest carrier said in a statement Wednesday. United Airlines began the only nonstop flight from San Francisco to Singapore on June 1. Such long-distance Asian routes are among airlines’ higher-yielding flights and cater to business customers in particular. The lack of a nonstop service has been a competitive disadvantage for Singapore Air, which now routes its U.S. flights to Singapore through other cities including Hong Kong and Frankfurt. The carrier halted direct flights to Los Angeles and New York in November 2013 as costs surged from using four-engine A340s on the all business-class services. “Nonstop operations are critical for us,” said James Boyd, a spokesman for Singapore Air in New York. “They are a staple for corporate travel that we’ve served for many years.” United said in an e-mail it is confident it will be “successful on this route,” with its San Francisco hub providing onward connections to more than 40 cities in the Americas. For a story on Singapore Air’s plan to resume the world’s longest flight, click here. The new 13,600-kilometer flight by Singapore Air could take between 14 hours and 35 minutes to 17 hours and 45 minutes depending on time and direction. It will be the carrier’s longest nonstop flight until services to Los Angeles and New York resume in 2018, when it receives a longer-range A350-900. The airline has seven of these aircraft on order. While the carrier will offer 253 seats in three classes on the route, there could be some capacity restrictions due to headwinds that will result in some seats not being offered for sale, Singapore Air said. United’s Singapore-San Francisco flight uses a Boeing Co. 787-9. The 8,446-mile (13,600-kilometer) route is the longest 787 flight, at almost 16 hours, and the longest by a U.S.-based airline, the carrier said at the time. United and Singapore Air are members of the Star Alliance airline partnership. They don’t use code-sharing on United’s San Francisco-Singapore flight, which would have enabled Singapore Air to sell seats on that service. The two airlines will continue to offer reciprocal passenger benefits such as frequent-flier miles awards and lounge access, a spokeswoman for the U.S. carrier said in an e-mail separately. Singapore Air also said it will end its service to Sao Paulo on Oct. 20, citing “sustained weak performance” of that route. The flight from Brazil, which is mired in a deep recession, is operated through Barcelona. Flights between the Spanish city and Singapore will continue.