United Airlines, once again, will have Oscar Munoz as its president and chief executive officer.

It was early in January when Munoz was hospitalized to undergo heart transplant surgery. Since then, he was on medical leave. Brett J. Hart, the airline's general counsel, is serving as acting chief to fill Munoz's role.

Munoz, 57, will return full-time on March 14, a day when United will hold a summit of its different labor unions, Bloomberg reported. The meeting was originally scheduled on Oct. 15, the day Munoz had a heart attack.

In a new video posted by United, Munoz told employees, "I cannot thank you enough for the incredible professionalism and commitment to your jobs that I've seen... I am energized by the momentum we have, now I'm ready to join you."

Munoz is participating in major decisions for the company and meeting with employees and shareholders even while he's on recovery. His efforts have solved some of the airline's problems.

United Airlines Facing Issues

J.D. Power's 2015 ranking labeled United's customer satisfaction as the worst among big North American airlines.

Some improvements, however, are being seen now that Munoz is CEO. The Chicago-based airline has reached a deal with its workers, such as finalizing a contract extension with its pilots union. Some issues still need resolving, though, as flight attendants continue to be divided between those who began with pre-merger Continental Airlines and those who started with pre-merger United.

Sara Nelson, international president of the Association of Flight Attendants, told Bloomberg that United's situation has been improved with Munoz's arrival as CEO. His sick leave didn't hinder Munoz from effectively performing his duties to the company.

United's on-time arrival and cancellation rates have been developed and are no longer inferior to Delta Air Lines Inc. and American Airlines Group Inc. In August, data from the U.S. Department of Transportation placed United at 10th place out of 13 U.S. carriers in on-time arrival rates. The airline's ranking reached no lower than sixth and sometimes outdid American.

"The board is confident in the strength and potential of United's business -- and very pleased Oscar will be returning," Henry L. Meyer III, non-executive chairman of United's board of directors, said in the statement quoted by the news outlet.

Strained Labor Relations

Munoz took over as CEO in September to boost morale after years of strained relations with its employees. He filled the position of Jeff Smisek, who stepped down during a federal investigation into United's relationship with the Port Authority of New York and New Jersey. Smisek, the former chief executive of Continental, was facing allegations that the airline had traded favors with the two cities.

Customers have criticized United's performance after its merger with Continental, according to a separate report from the New York Times. Angered passengers have complained of delays, computer issues and problems in its reservation system.

In February, it was reported that the International Brotherhood of Teamsters representing United maintenance workers and mechanics rejected the airline's final contract offer, prompting possibilities of a strike.

Yet with Munoz's comeback, United may be up for greater heights. To employees, he ends his return announcement, "Let's fly safe and take care of each other."