The CEO of United Airlines, who has been on medical leave since suffering a heart attack in October, underwent a heart transplant on Wednesday. The airline said that he is recovering.

United said that it expects Oscar Munoz to return to work this spring. The airline said that a transplant was “considered the preferred treatment and was not the result of a setback in his recovery.”

It did not provide more details, including where the transplant was performed. It promised to provide more information within 24 hours.

Munoz, 57, became CEO in early September after Jeff Smisek abruptly stepped down during a federal investigation into the airline’s dealings with officials who run airports in the New York City area, including Newark, New Jersey, where United has a major hub.

Munoz suffered a heart attack in mid-October, although the company declined to confirm it for several days. At the time, United would only say that Munoz was in the hospital. On Oct. 19, United announced that Munoz would take medical leave, and general counsel Brett Hart was named acting CEO.

In November, Munoz visited United’s operations center and said that after talking with doctors he planned to return to work in the first three months of 2016. On Wednesday, United said it expects him back by the end of the first quarter, March 31, or early in the second quarter.

There were 2,331 heart transplants last year in the U.S., according to the United Network for Organ Sharing, which manages the waiting list and tracks transplants.

About 88 percent of patients survive for one year, and 75 percent for five years, according to the National Heart, Lung and Blood Institute.

Medical authorities say patients may return to work in two to three months, although that varies by age and the presence of other medical problems.

“We have seen patients who are very motivated go back to high-stress jobs earlier, but it is very individualized,” said Dr. Mario Deng, medical director of the heart-transplant program at the medical center at the University of California, Los Angeles. “Medically speaking, it’s possible if there is no rejection and the (new) heart performs well.”

United’s sparse information about Munoz’s health has renewed a debate about how much companies should disclose in such cases. Publicly traded companies must disclose a change in leadership but have leeway in deciding how much to disclose about an executive’s health.

Companies have leaned toward more disclosure since Apple Inc. was criticized for failing to fully inform shareholders about CEO Steve Jobs’ health before he died in 2011 from pancreatic cancer.

During his brief CEO tenure, Munoz acknowledged that United had failed its customers by subjecting them to chronic delays and computer outages, and he sought to improve relations with employees.

Munoz was the chief operating officer of freight railroad CSX Corp. before replacing Smisek on Sept. 8. Munoz had previously worked at AT&T, Coca-Cola and PepsiCo and served on the boards of Continental Airlines and, after their 2010 merger, United Continental Holdings Inc.

Chicago-based United is the world’s second-largest airline behind American Airlines.

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David Koenig can be reached at http://twitter.com/airlinewriter