By Sweta Singh and Jeffrey Dastin
(Reuters) - United Continental Holdings Inc
Munoz's health issues are the latest setback for the No. 2 U.S. airline in terms of seat capacity, which last month named the former CSX Corp
United's shares were down 3.4 percent in afternoon trading. They have dropped nearly 17 percent so far this year.
In a statement on Friday, the airline said Munoz, 56, had been hospitalized on Thursday, but did not provide further details about his condition.
"Our thoughts and prayers are with his family and we are respecting their privacy," the carrier said in a statement, adding it was operating normally.
The Wall Street Journal reported on Friday that the company's board was waiting to hear from doctors and from Munoz's family about the severity of the heart attack he had suffered, before deciding if an interim leader was necessary.
Smisek had stepped down amid investigations surrounding United's dealings with the Port Authority of New York and New Jersey, but the airline had also struggled under his leadership to merge the operations of the former United and Continental airlines.
United Continental has been beset by complaints by customers and employees in recent years, and Munoz has made tackling them a top priority.
Shortly after taking over, Munoz told the company's employees in a letter that he would meet with as many workers as possible and "hear about operations directly from you."
He had called a meeting of United's union leaders for Thursday, but a United spokeswoman said those talks did not take place.
The Wall Street Journal cited an "informed individual" as saying the heart attack may have been mild and that Munoz could be back at work in two weeks.
(Reporting by Sweta Singh in Bengaluru and Jeffrey Dastin in New York; Editing by Christian Plumb, David Gregorio and Bernadette Baum)
