Warren Buffett’s decision to take stakes in the four largest U.S. airlines could be a first step to eventually taking over one of the companies, analysts said, citing his history in the railroad industry.

“We view a full-scale acquisition of an airline by Berkshire as a possibility and not worth dismissing, particularly if the stocks weaken,” Morgan Stanley analysts led by Rajeev Lalwani said in a note to clients Wednesday.

Buffett’s Berkshire Hathaway Inc. jumped into airline stocks in the second half of 2016, becoming one of the top two investors in Delta Air Lines Inc., United Continental Holdings Inc., American Airlines Group Inc. and Southwest Airlines Co. While the move surprised observers who were accustomed to the billionaire’s skepticism about the business, Berkshire Vice Chairman Charles Munger has likened his company’s new stance to its shift on railroads a decade ago.

“It was a terrible business for about 80 years,” Munger, 93, said at an event last week in Los Angeles. “But finally they got down to four big railroads and it was a better business. And something similar is happening in the airline business.”

Berkshire paid more than $26 billion in the 2010 buyout of Burlington Northern Santa Fe, acquiring the 77.5 percent of the railroad that it didn’t already own. Buffett had previously purchased minority stakes in BNSF, Union Pacific Corp. and Norfolk Southern Corp. After the BNSF deal, he sold the stocks of its rivals.

‘Certain Romance’

While survivors in the rail and airline industries both benefited from consolidation, Buffett has pointed to differences. The billionaire told Charlie Rose in an interview last month that it could be relatively easy for a newcomer to buy and move planes, when compared with the expense of laying train tracks across thousands of miles. Beyond that, the airline industry has an appeal that tends to attract upstarts, regardless of the economics.

“There’s a certain romance to it,” Buffett told Rose, likening the business to Hollywood. “There’s no question that it’s been a graveyard for a lot of money.” Buffett wasn’t asked on the show about whether he’d buy an airline outright, and didn’t return a message Wednesday left with an assistant seeking comment.

Buffett has made other bets on the long-term trend of more air travel. Omaha, Nebraska-based Berkshire’s only purchase that rivaled BNSF in size was the acquisition last year of Precision Castparts, a manufacturer of airplane parts.

The six biggest U.S. carriers -- bolstered by lower jet-fuel prices and years of dealmaking that left fewer major competitors -- posted their fifth straight year of profits in 2016, earning about $14 billion on an adjusted basis, according to data compiled by Bloomberg. That followed more than $50 billion of losses in the previous decade.

‘For the Better’

Representatives from Delta, United, American and Southwest didn’t immediately respond to messages seeking comment.

“While we have no knowledge of any potential transactions, U.S. airlines have structurally changed for the better following consolidation that has resulted in more pricing power, supply discipline, and a focus on margins over market share,” Morgan Stanley’s Lalwani wrote. “An interest in industries with structural improvement and the gradually growing stakes are fairly consistent with Berkshire’s approach to acquiring Burlington Northern Santa Fe.”

Berkshire had more than $80 billion in cash as of Sept. 30. And Kraft Heinz Co., the food company that Buffett controls with 3G Capital, recently abandoned its pursuit of Unilever.

Cowen & Co. told investors as well not to rule out the chance of Buffett buying an airline, and also raised the possibility of a leveraged buyout.

“Every year there is a surprise in the industry,” Cowen’s Helane Becker said in a note this week. “This year, we believe a surprise may be that a major airline gets acquired, potentially by Berkshire, or goes private on its own. Airlines are labor intensive and capital intensive, so they don’t make the best LBO candidates, but stranger things have happened.”