The company reported a 7% fall in profits for the first half of the year.
It added average fares had dropped 3% over excess capacity in Europe and due to an earlier Easter in the first quarter.
Bosses also blamed repeated strikes and staff shortages, which led to a surge in cancellations for higher fare, weekend flights.
Chief executive, Michael O’Leary, said: “As recently guided, H1 average fares fell by 3%.
“While ancillary revenues performed strongly, up 27%, these were offset by higher fuel, staff and EU261 (compensation) costs.