More than a month after stepping back to recover from pneumonia and leg surgery, Canadian Pacific Railway Ltd.'s chief executive officer Hunter Harrison is waiting for doctors to clear his return to full-time work.

Mr. Harrison said in late July he would hand his daily responsibilities to Keith Creel, chief operating officer, and limit travel between the United States and Calgary while recovering from complications from surgery to improve blood flow in his legs. A CP spokesman said doctors have not yet cleared Mr. Harrison to return to work full time.

Mr. Harrison, who is in his early 70s, flew to Calgary two weeks ago and is working with the company's leadership, said Martin Cej, a spokesman for CP Rail. He is splitting his time between Connecticut and Florida while keeping tabs on the railway's operations. "He's very much involved day-to-day. Things are coming along exactly as planned," Mr. Cej said.

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News of Mr. Harrison's health troubles in July was followed by an announcement that his counterpart at Canadian National Railway Co. would also take time off to handle medical troubles.

Claude Mongeau, CEO of Montreal-based Canadian National Railway, underwent surgery on Aug. 25 for a "precancerous" throat tumour. Chief financial officer Luc Jobin is taking the leadership role at CN in Mr. Mongeau's absence, which is expected to last three months. A CN spokesman described the operation as successful.

Mr. Harrison became CEO of CP in 2012 after U.S. investor Pershing Square Capital Management won a battle for control of the boardroom. He has been credited with driving a resurgence at CP, slashing costs and improving network efficiency as the stock price soared and profits set company records. Before coming to CP, he was credited with turning around CN and Illinois Central.

Christian Wetherbee, an analyst with Citigroup, said Mr. Harrison is known for being a good motivator who can hold people to high operational standards, but his absence is not having a great an impact on the company, given Mr. Creel has been implementing Mr. Harrison's vision for how the company should be run.

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"Keith [Creel] is a great operator in his own right but Hunter is Hunter. There is a reason why Pershing chose him to be the face of their proxy battle against the old management team," Mr. Wetherbee said.