Ryanair, Europe's biggest budget airline, has warned that profit growth will slow because of higher airport taxes and duties on passengers.
Ryanair says it will keep up its price war in order to attract travellers
The news sent Ryanair's shares almost 8% lower, and came as the company reported record profits for the year running to the end of March.
Ryanair announced that its annual post-tax, adjusted profit jumped 33% to 401.4m euros (£272m; $542m).
However, it warned growth would slow to 5% in the current financial year.
The airline urged shareholders to remain "cautious and conservative".
Ryanair's shares ended Tuesday trading down 7% to 5 euros.
Ryanair's chief executive Michael O'Leary told the BBC that a number of factors had combined to slow earnings growth.
Mr O'Leary complained that "swingeing price increases imposed at Stansted airport, where costs have doubled since April", and higher air passenger duties (APD) were having a negative impact on demand.
The company also singled out Dublin airport for criticism, accusing both it and Stansted of imposing unjustified price increases while providing substandard service and facilities.
"These monopoly price increases demonstrate again the abject failure of aviation regulators in both Ireland and the UK to protect the interests of consumers," Ryanair said.
The airline added that it would continue to press for the break up of BAA, the company that runs the UK's biggest airports, including Heathrow, Gatwick and Stansted.
Despite the problems, Ryanair has benefited from its decision to start charging customers for every bag that they check in, and for services such as priority boarding.
Ryanair said that its average fare per customer rose by 7% in the 12 months to the end of March, while its total traffic figure climbed by 22% to 42.5 million people.
The company added that its ancillary revenues increased by 40% over the past financial year "thanks to better passenger spend, increased penetration, and the growth of excess baggage revenues".
Even so, Ryanair warned that forward bookings and yields would be under pressure, and it planned to continue its "price war".
"This remains an extremely volatile and cyclical business," Ryanair said.