Threatened strike action in March has worsened losses at Aer Lingus in the first quarter.
The airline has reported operating losses of €48.5 million, €3 million worse than the same period last year.
The result was also blamed on the later timing of Easter this year.
"This threatened action resulted in the cancellation of flights in advance of St. Patrick’s weekend as well as the forced re-booking and re-accommodation of a significant number of passengers," it said.
Although the strikes were called off, Aer Lingus had already cancelled 29 flights and hired 16 extra aircraft as a back-up.
The airline is due to unveil details of a two-year cost cutting programme later this month.
Chief executive Christoph Mueller said: "The need to maintain our differentiation and tightly manage our cost base is very clear to us.
"Our short haul operation remains an attractive and profitable business despite the continuation of intense price competition in European markets.
"Forward trends are positive, especially in long haul. We continue to expect that our operating result for 2014 will be broadly in line with 2013."
