Ryanair's profits collapsed 21% fall in profits to €243 million (£219 million) in the first three months of the financial year.
The low-cost airline said lower fares and higher costs for fuel and staff were behind the drop off.
Chief executive Michael O'Leary said: "The two weakest markets were Germany, where Lufthansa was allowed to buy Air Berlin and is selling this excess capacity at below cost prices, and the UK, where Brexit concerns weigh negatively on consumer confidence and spending."
The airline said its average fares were 6% cheaper over the quarter, but this was partially offset by 14% incomes for extras like baggage and food.
And delays to its new planes aren't helping.
"We expect traffic to grow by 7% to over 152million, slightly less than the 153million previously guided due to the Boeing MAX delivery delays," O'Leary said.
But despite the drop, Ryaniar still predicts it will finish the year with between €750million and €950million profits after tax.
However, things could change if fares stay low, with O'Leary also pointing out there were risks from "security events" as well as "negative Brexit developments" in the second half of the year.
Hargreaves Lansdown equity analyst George Salmon said: “Profits may be down, but that’s something of an inevitability given the headwinds of increased fuel prices and the acquisition of Laudamotion, where costs haven’t been managed as effectively.
"As it turns out, a 21% fall in after-tax profit is better than had been expected by many analysts."
He added: "The problem is airlines are always going to be plugged in to the wider economy, and the UK’s upcoming departure from the European Union, possibly without a deal, means the near-term is still shrouded in uncertainty."
But things are a lot better there than at other airlines. "Ryanair should be able to improve performance at Lauda, and the expectation is demand for low-cost air travel will grow over time," he said.
"The group has a strong balance sheet and can point to a solid track record of winning market share and keeping costs down."
