Ryanair posted a net loss of €19.6m (£17.2m) for the last three months of the year as fierce competition forced it to cut fares.
The airline carried 32.7 million passengers compared with 30.4 million for the same period a year earlier as revenue rose 9% to €1.53bn.
But the airline said “excess winter capacity in Europe” cut its profit.
The company said chairman David Bonderman will leave in the summer of 2020.
In September, at the firm’s annual meeting, almost 30% of shareholders voted against the re-election of Mr Bonderman as chairman after a summer of flight cancellations. He has spent 22 years in the job.
Chief Executive Michael O’Leary has agreed a new five-year contract , the firm said.
Mr O’Leary, who has been chief executive for 24 years, told the same annual meeting he had concerns about committing to a contract of that length, telling shareholders: “I’m not sure Mrs O’Leary would be happy.”
He said the loss was “disappointing”, but “we take comfort that this was entirely due to weaker than expected air fares”.
While higher oil prices and lower fares cut the firm’s profitability, they were creating even bigger problems for rivals, Ryanair pointed out.
Firms like Wow, Flybe and Germania are seeking buyers.