Ryanair has said recent pilot and cabin crew strikes are partly to blame as it cut its profit expectations by as much as 12%.
The airline said it now expects profits in the range of €1.1m - €1.2m for the year to the end of March – down from the previous guidance of €1.25bn to €1.35bn.
The airline said that staff unrest, alongside an increase in the price of oil globally are to blame.
Shares in the airline fell 10% after it issued the warning.
The company said it could not rule out further reductions in its profit outlook over the coming months.
It said weaker passenger traffic and lower fares in September were caused by two days of coordinated pilot and cabin crew strikes in Germany, the Netherlands, Belgium, Spain and Portugal.
It said forward bookings for half-term and Christmas had been affected by customer concern over the risk of further industrial action.
The airline also had to shoulder the cost of re-accommodating passengers who were affected by the various strikes.
At the same time, the airline has faced rising fuel costs with the price of oil climbing to a near four-year high at more than $80 a barrel.
Announcing the reduction, the company claimed the recent strikes were “incited by competitor employees despite the fact that Ryanair has agreed to meet union demands for local contracts, local law, and a five-week arbitration with pilots in Germany when the VC Union sought a prolonged five month arbitration.”
The company’s CEO Michael O’Leary said although the company had “successfully managed the strikes," passenger numbers were still affected.
“While we regret these disruptions, we have on both strike days operated over 90% of our schedule,” he said.
“However, customer confidence, forward bookings and Q3 fares have been affected, most notably over the October school mid-terms and Christmas, in those five countries where unnecessary strikes have been repeated.”
In response to the drop, the company has announced plans to trim back its winter flight schedule by 1% and close its bases in Eindhoven and Bremen.
The airline said most routes would continue to and from both cities.
Meanwhile, it has reduced the number of aircraft at its Niederrhein base from five to three.
It said all affected passengers have been notified by email or text message this morning.
Meanwhile, the company has pledged to consult with pilots and cabin crew at the three affected bases in an effort to “minimise job losses.”
Ahead of the announcement of its half-year financial results later this month, it said its fares for the summer quarter were down 3% - compared to a previous guidance of a 1% rise.
It said it cannot rule out further profit reductions, “which may require full year guidance to be lowered further and may necessitate further trimming of loss making winter capacity.”