Ryanair delivered a 6% increase in net profit to a record €1.3 billion for the year to the end of March.
The airline said it had experienced "difficult trading conditions" due to the impact on tourism and travel plans caused by terrorist attacks in a number of European cities and the devaulation of sterling after the Brexit vote.
Ryanair warned that a "hard" Brexit, a scenario in which the UK leaves the European Union without agreeing a trade deal with the bloc, could cause "significant disruption to UK/EU flights for a period of months after March 2019".
"In the absence of such certainty, or direction, we will continue to pivot our growth away from the UK in 2017 and 2018 to capitalise on the many growth opportunities elsewhere in Europe," it said in a statement alongside the results.
Ryanair's chief commercial officer David O'Brien said the company remains sceptical that the UK can stay in the EU Open Skies system after Brexit.
Speaking to Morning Ireland on RTÉ Radio 1, he said there will be considerable disruption to EU/UK flights if the UK exits the system when it leaves the UK in March 2019.
If that happens, he said, Ryanair is confident it can redistribute aircraft from the UK to other countries.
"We have 86 bases across the Ryanair network. 73 are non-UK. We have around 80 aircraft in UK. When you look at it across its entirety, it's not as big a deal as it seems. That's one aircraft for every base. All our bases are seeking more than one aircraft for their own growth," he explained.
Ryanair carried 120 million passengers last year, up 13% on the previous 12 months. Revenue rose by 2% to €6.65 billion. During the financial year it filled 94% of the seats on its flights.
Average fares fell by 13% to €41 as the airline said it passed on savings due to falling fuel costs.
The airline also said its costs were cut significantly by the fall in the value of sterling over the past year.
Looking ahead, Ryanair said it expects to gain significant savings from new more fuel efficient planes with more seats and from a five-year pay deal with staff.
It said it expected to increase its net profit in the current year by around 8% to between €1.4-1.45 billion by adding an additional 10 million seats of capacity while allowing fares to fall by a more modest 5-7%.
The airline also said its "Always Getting Better" programme to improve customer service, which also involved a significant investment in its online and ecommerce operations, has boosted non-ticket or ancillary revenues.
Ryanair said its mobile app has been downloaded more than 20 million times and that it now has 20 million MyRyanair members who have signed up through its website.
After years of falling ticket prices, some rival European carriers in recent weeks have reported seeing signs of a turnaround as the decline in fares slows.
British Airways owner IAG had said before it was hit by a disastrous IT failure at the weekend that it expected quarterly revenue per passenger mile flown to register its first year-on-year increase since 2014 in the three months to the end of June.
Air France and Lufthansa have also said that the pricing environment and bookings are improving heading into the summer.
"We are maybe a little less optimistic than some of the other airlines out there on pricing but we are all singing the same tune," Ryanair's chief financial officer Neil Sorahan said.
Ryanair's cost base, already the lowest in the industry, fell 5% last year after fuel price falls were excluded and will fall a further 1% this year, Neil Sorahan said.
In a sign of Ryanair's financial confidence, he announced a new €600m share buyback to start immediately.
However, O'Leary warned that there were a number of potential clouds on the horizon, including Brexit negotiations which he has said could lead to a total breakdown in all flights between Britain and the EU for a time.
"We are pleased to report a 6% increase in profit after tax, despite difficult trading conditions caused by a series of security events at European cities, a switch of charter capacity from North Africa, Turkey and Egypt to mainland Europe, and a sharp decline in Sterling following the June 2016 Brexit vote," CEO Michael O'Leary said in a statement.
"Investors should be wary of the risk of negative Brexit developments, or any repeat of last year’s security events at European cities, which could damage consumer confidence, close-in bookings and this FY18 guidance," he added.
Ryanair shares closed 3.7% higher in Dublin trade today.
