U.S. airlines have had trouble this year convincing investors that they’re leaving their boom-and-bust cycle behind. Now the industry has won over one of its biggest skeptics. Berkshire Hathaway Inc.’s investment in the four biggest carriers ended years in which billionaire Chairman Warren Buffett derided the industry’s attractions. The company revealed stakes this week in American Airlines Group Inc., Delta Air Lines Inc., United Continental Holdings Inc. and Southwest Airlines Co., the remaining carriers after years of dealmaking that cut the number of major players by more than half. Consolidation and falling jet-fuel prices pushed earnings at the six biggest U.S. airlines to a record $18.4 billion in 2015, the industry’s fourth straight year of profitability following a decade in which combined losses climbed to $53 billion. The turnaround prompted American’s chief executive officer, Doug Parker, to say the industry’s traditional boom-bust cycle is giving way to an era of steady returns. “People still have the thought that you rent airlines, you don’t own them,” said Craig Hodges, CEO of Hodges Capital Management Inc., which has held airline shares since 2011. “Buffett is saying, ‘No, you own them.’ That’s a sea change in investor sentiment that’s just starting.” The Bloomberg U.S. Airlines Index climbed 2 percent at the close in New York, continuing its longest winning streak since February. As of the end of last week, the index had declined slightly this year amid increased capacity of flights and seats and sustained declines in revenue for each seat flown a mile. ‘Still a Skeptic’ Not everyone agrees that this time is different. While fundamentals for the industry look better now than they have in a long time, doubt remains about airlines’ ability to withstand a serious downturn, said Alan Bender, chairman of the social sciences and economics department at Embry-Riddle Aeronautical University. “Long term, I am still a skeptic,” Bender said. “Given the history of the airline business, there have been periods where they looked pretty darn good and a few years later they were back in the dumps again. It would seem different this time, but I wouldn’t put all my chips on that.” Buffett used to be a skeptic, too. He called the airline industry a “death trap for investors” according to a 2013 interview with TheStreet.com. More than a decade before that, the billionaire said he’d sworn off investing in carriers after lamenting the “mistake” of betting on USAir in 1989. He’s credited with saying if a capitalist had been at Kitty Hawk in the early 1900s “he should have shot Orville Wright. He would have saved his progeny money.” ‘Anchor Tenant’ United CEO Oscar Munoz, speaking Tuesday to investors and analysts in Chicago, called Berkshire “the anchor tenant,” and said its share purchase reflected faith in United and the overall industry. In a statement Monday, Delta said it “welcomes new investors as we continue to build a model for sustainable, long-term success as a high-quality global company.” American said the investment “further reinforces our view that our industry has fundamentally changed in a profound and lasting way.” Savanthi Syth, a Raymond James Financial Inc. analyst, echoed the opinion that Berkshire’s investment signals a belief that the industry can weather a downturn and provide stronger shareholder returns over an economic cycle. “Moreover, it is likely to provide credibility to a potential re-rating of valuations closer to that of high-quality industrials in an era of stronger balance sheets and largely disciplined, through still highly competitive, behavior,” Syth said in a note to investors.