Ethiopian Airlines CEO Tewolde Gebremariam, who transformed the airline into Africa’s biggest carrier, said on Wednesday he had resigned to focus on his medical treatment.

In an internal memo to employees seen by Reuters he said he had had health issues for almost a year and had been working from the United States for the past five months and was not able to return to the head office any time soon.

“I am retiring early due to health issues,” he told Reuters in a text message, echoing the language in the memo which said he would focus on his treatment.

In his 11 years at the helm, Tewolde grew the carrier from just 33 planes into a fleet of 130 planes operating on local and international routes, and from 3 million passengers to 12 million passengers, pre-COVID, the airline said in a statement.

“Mr. Tewolde led the airline for over a decade with remarkable success reflected in its exceptional performance in all parameters including but not limited to exponential growth from 1 billion USD annual turn-over to $4.5 billion,” the state-owned carrier said.

“Under his leadership, the airline group has grown by four fold in all measurements.”

The airline confirmed the board had accepted his request for early retirement and said a successor would be announced shortly.

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