United Continental CEO Oscar Munoz had a heart attack on Thursday and is currently in a Chicago hospital, Dow Jones reported Friday.
The report, citing a person familiar with the matter, said the company's directors were waiting to hear about the severity of the attack. Depending on that information, they would decide whether United would need an interim chief, according to Dow Jones.
"We have been informed by Oscar's family that he was admitted to the hospital on Thursday, and we will provide further details as appropriate. In the meantime, we are continuing to operate normally," United said in a Friday afternoon statement. "Our thoughts and prayers are with his family and we are respecting their privacy."
Shares in the company's stock dipped on the news.
United tapped Munoz to take over as CEO after it ousted Jeff Smisek in September amid a probe into improprieties at the Port Authority of New York and New Jersey. Smisek, who was chairman, president and chief executive, received about $4.9 million as a separation payment.
In a letter to employees after the CEO switch announcement, a copy of which was obtained by CNBC, Munoz said he planned to meet with staff to figure out how the company could operate better and improve customer service.
Before coming to United, Munoz served as the COO of CSX. He is credited in part for changes that made that company an industry leader in safety and steadily improving financial performance, people familiar with his tenure said.
Munoz had held finance jobs at consumer products companies including Coca-Cola , AT&T and Pepsico before joining CSX.
—Reuters contributed to this report.