Avianca was a failing airline with 37 outdated planes when German Efromovich purchased it out of bankruptcy in 2004. Over 15 years the Bolivian businessman built it into a regional powerhouse as Latin America’s second-largest carrier.

But for all its success, the Bogota-based company is now back on a rocky foundation. Its stock price is down by almost 75% since it went public in 2011 and its bonds are trading in distressed territory amid concerns it will struggle to refinance debt. Avianca’s first-quarter loss was the biggest since 2015.

The man most responsible for the mess is the same who so recently was treated as a hero—Efromovich.

The self-made millionaire imperiled the airline’s future by last year offering up his 51.5% stake in Avianca as collateral on a loan from United Continental Holdings Inc. His holding company BRW Aviation quickly breached terms of the contract and, as a result, control of Avianca could pass to United’s hands. While that would likely be a positive for Avianca’s minority shareholders and bondholders, the current uncertainty has created myriad problems for the airline just as it faces down a $550 million bond coming due next year.

“We’re very worried by the company’s instability at the moment,” said Jaime Hernandez, president of the Colombian pilots’ union ACDAC, which in 2017 went on strike for almost two months over a wage and benefits dispute. “We were a great company and the management of it recently has been very bad for our operations, our reputation.”

Efromovich, who is also Avianca Holdings SA’s chairman, said in a radio interview in Bogota on Tuesday that there was no possibility of United taking over anytime soon. Avianca’s situation was “controlled,” he told Blu Radio.

In a written response to questions from Bloomberg, he denied that problems at his other businesses are creating risks for Avianca, which isn’t party to the loan. “Everything is aligned with United as per the loan agreement. There is nothing to rectify,” he wrote.

United says it hasn’t seized the Avianca shares and is working with BRW.

But it’s an option it could exercise at any point. Doing so would trigger change-of-control provisions on various loans that could force the airline to come up with roughly $1.5 billion to pay off creditors, according to analysts at Bogota-based brokerage Corredores Davivienda. That’s more than four times the amount of cash it had on its balance sheet at the end of the first quarter.

Even if United doesn’t take control, just the fact that it could do so complicates Avianca’s efforts to operate and raise financing. Investors are hesitant to lend to a company that could at a moment’s notice be on the hook for a bunch of money that it doesn’t have.

Chief Financial Officer Roberto Held said Avianca is working urgently to amend loan contracts to account for the situation and still plans to sell bonds this quarter to pay off notes due next year. Meanwhile, it’s sticking to a business plan focused on cutting debt and increasing profitability by selling assets, canceling aircraft orders and scrapping some routes.

The tumult couldn’t have come at a worse time for Avianca. It has been buffeted by surging fuel prices this year along with weaker Latin American currencies and less demand for air travel amid slowdowns in the region’s biggest economies. Chief Executive Officer Hernan Rincon quit in April. And low-cost carriers are adding competition.

Avianca is only the latest difficulty for Efromovich, who has seen parts of the sprawling Latin American conglomerate he built with his brother, Jose, unravel in recent years. His shipyards have shut down. His Brazilian airline was forced to seek court protection from creditors. And now he’s at risk of losing Avianca.

It’s quite a turnaround from 2004, when Efromovich was lauded across Colombia for rescuing the world’s second-oldest airline. (Its first flight was in 1920, ferrying passengers between the municipalities of Barranquilla and Puerto Berrio.) Previously owned by the country’s richest family, it was hemorrhaging money in the wake of the Sept. 11 terrorist attacks and the global recession that followed.

Efromovich bought it out of Chapter 11 for $64 million and an assumption of debt. A mechanical engineer by training who got into the aviation business in Brazil, Efromovich doubled the number of aircraft Avianca operated and soon started turning a profit. By last year, Avianca’s 190 aircraft were carrying 30 million passengers, second only to Latam Airlines in the region.

Former President Alvaro Uribe, who granted Efromovich Colombian citizenship in 2005, was among his biggest fans. “We Colombians admire you, we appreciate you, we value you, we consider you an example” of the type of investor the country needs, he said in 2010 when Efromovich received a “businessman of the year” award from newspaper La Republica.

Efromovich’s personal fortune began to turn in 2014, at the start of Brazil’s worst recession on record. He took a loan from Elliott Management to prop up his shipyard business there, which ended up closing.

Meanwhile, Efromovich moved ahead with expansion plans for Avianca, forming a joint venture with United and Panama’s Copa Holdings in which the three airlines would coordinate routes and schedules. Related to the deal, Efromovich’s BRW Aviation borrowed $456 million from United to pay off loans taken by his Brazilian businesses, using his stake in Avianca as collateral.

In April, Avianca said in a regulatory filing that BRW Aviation was in breach of a collateral coverage term of the United loan. That was partly because Avianca’s share price plummeted, causing its market capitalization to dip to $510 million by the end of 2018.

The possibility of a change in control has forced Avianca executives to seek to amend agreements to list United as a potential controlling shareholder. In addition to the bonds due next year, Avianca owes roughly $800 million to European export credit agencies, quasi-government financial institutions that secure funding for exporters, among other debts, according to executives.

Avianca needs to update loan contracts to include United as a potential controlling shareholder “to prevent a breach of the company’s financial commitments,” S&P Global Ratings said in a May 13 note. It downgraded the debt rating further into junk territory, the CCC+ level, citing “higher refinancing risk” due to BRW’s breach.

Of course the loan isn’t Avianca’s only headache, and some observers say Efromovich is getting too much of the blame for the company’s woes.

“The current problems are in good part due to Avianca, a business that has had bad numbers in recent quarters,” said Carlos Enrique Rodriguez, an analyst at Bogota brokerage Ultraserfinco who recommends selling the shares. “Corporate governance has been questioned and that has affected the stock price. But to say Avianca’s problems are all the fault of Efromovich is not entirely fair.”

In the long term, a change in control to United could be a positive for Avianca, said Gimme Credit analyst Cedric Rimaud, who recommends buying the bonds.

“There is still one year before the bonds come due and a lot can happen until then,” he wrote in a report. “If United takes over the control of the company, it will be a very positive news for bondholders, as the credit profile would improve markedly.”

But for now, investors seem doubtful of Avianca’s prospects.

The rating downgrade accelerated a sell-off in the bonds that began at the end of April. The notes due next May now trade at about 88 cents on the dollar, pushing the yield to 23%, according to Trace bond trading data. It’s among the worst performers this year in the Bloomberg Barclays Emerging Markets Corporates bond index.

“At first the assumption was that the problems were isolated” to just Efromovich and his outside businesses, said Roger Horn, a senior emerging-markets strategist at SMBC Nikko Securities America in New York. “But everything becomes a factor when an emerging-market company is looking to refinance a $550 million bond.”