United Airlines’ general counsel Brett Hart (pictured) is to step up to the role of acting chief executive.
The announcement came four days after chief executive Oscar Munoz was admitted to hospital having suffered a heart attack.
The airline said it was too soon to know the course of treatment Munoz will take or the timing of his recovery.
Hart vowed to continue an agenda set by Munoz that has been aimed at rebuilding the company’s morale after years of strained labour relations.
United said that its board “remains actively engaged in preparing for all potential outcomes regarding the company’s leadership structure.”
Hart is due make his first presentation to investors as acting chief on Thursday, when the carrier reports third-quarter results.
He will work closely with board chairman Henry Meyer and United’s executive team to run the company in Munoz’s absence.
Mayer said: “Brett has taken on increasing responsibility beyond general counsel over the last few years in the operations and customer facing areas of the company.
“I am confident in his ability to continue to implement the company’s strategy and Oscar’s mission of bringing United’s people together around the shared purpose of becoming the best airline for our customers and employees.”
Hart said: “Oscar’s agenda is focused on customer service, teamwork and innovation and I, along with the executive team, will continue to move quickly to implement it.
“We believe strongly that we can continue to make steady progress on increasing shareholder value by working together to deliver a great product to our customers.”
Hart joined United in 2010 after working as general counsel of consumer goods company Sara Lee Corp.
Munoz became chief executive in September after predecessor Jeff Smisek resigned in relation to internal and federal probes into United’s relationship with the Port Authority of New York and New Jersey.