(Reuters) - United Continental Holdings Inc <UAL.N> Chief Executive Oscar Munoz suffered a heart attack and is in a Chicago hospital, The Wall Street Journal reported on Friday.
The company's board is waiting to hear from doctors and Munoz's family about the heart attack's severity before deciding if an interim leader is necessary, the report said.
United did not immediately respond to a request for comment.
United's shares were down more than 2 percent.
Munoz took the helm of the second-largest U.S. airline by capacity last month. He replaced Jeff Smisek, who resigned because of internal and federal investigations into the carrier's relationship with the Port Authority of New York and New Jersey.
The probes have focused on whether United added direct flights to Columbia, South Carolina to curry favor with the Port Authority's then-Chairman David Samson, who had a home there, a source familiar with the matter has said.
Munoz had called a summit of United's union leaders for Thursday and has made a point since taking the job of listening to customers and meeting with workers.
(Reporting by Sweta Singh in Bengaluru and Jeffrey Dastin in New York; Editing by Saumyadeb Chakrabarty and Christian Plumb)