Southwest Airlines Co. will join other U.S. carriers in reducing flights to Cuba, saying laws that restrict Americans from traveling to the island for tourism are constraining demand. Southwest becomes the latest airline to accept that the industry, with little way to judge demand beforehand, was too optimistic when U.S. regulators allowed passenger routes to the island nation last year for the first time in decades. President Donald Trump added to the woes earlier this month by announcing restrictions that may stall U.S. business in Cuba. The new limits don’t change airline operations but may affect demand. “Commercial airlines had not been involved in the Cuba market since before 1959,” said Tom Popper, president of tour operator InsightCuba. “It’s a natural shift in a marketplace where there was no historical data and a lot of unknowns, but everybody went in full force. You make the best predictions you can, try it and make adjustments as time goes on.” American Airlines Group Inc. and JetBlue Airways Corp. previously trimmed their service to Cuba, while Spirit Airlines Inc., Frontier Airlines Holdings Inc. and Silver Airways Corp. pulled out completely. Southwest will drop service to Varadero and Santa Clara on Sept. 4, and continue flying to Havana twice daily from Fort Lauderdale-Hollywood and Tampa airports in Florida, the carrier said in a statement Wednesday. “Our decision to discontinue the other Cuba flights comes after an in-depth analysis of our performance over several months which confirmed that there is not a clear path to sustainability serving these markets, particularly with the continuing prohibition in U.S. law on tourism to Cuba for American citizens,” Steve Goldberg, senior vice president of ground operations, said in the statement. Assessment Period Southwest Chief Executive Officer Gary Kelly previously said he would give the Cuba markets a year before deciding on continuing service. The Dallas-based carrier began flights to Varadero in November and to Santa Clara in December. The airline is contacting customers holding travel reservations for those cities on Sept. 5 and beyond to offer refunds. Southwest is seeking U.S. approval for a third daily Havana-Fort Lauderdale flight from among those given up by airlines that have left the island. American, JetBlue, Delta Air Lines Inc. and United Continental Holdings Inc. also are trying to secure those routes.