This came as the impact of a weaker euro more than offset gains from a rise in passenger numbers, the company said.
The airline posted a pretax loss of 8.59 million euro (9.79 million dollars) in the nine months to 31 December, compared with 5.73 million euro profit during the same period a year earlier.
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Total revenue rose to 352.90 million euro, from 345.82 million euro.
“The result of the nine months period under review has been significantly impacted by the depreciation of the euro,” the airline said in a statement.
Air Mauritius said the number of passengers carried rose 2.5 per cent to 1,016,314, against 991,907 a year ago.
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Mauritius is a popular holiday destination, but the fragile economic situation in its core European market and the depreciation of the euro against the dollar has hit the airline and the island's tourism industry.
Shares in Air Mauritius were unchanged at 17 rupees.