Ryanair shares tumbled nearly 5% after the airline reported its weakest annual profit in four years and said its earnings may suffer for the next couple of years due to continually low fares.
However, chief executive Michael O'Leary said shareholders should expect this and said fares should rise after continued consolidation in the European aviation market.
He also said Ryanair is well-placed for what he called "attritional fare wars" as the airline has "the lowest cost base".
"We expect further consolidation and airline failures in winter 2019 and again into 2020 due to over-capacity, weaker fares, and higher oil prices, particularly among those airlines who are significanly unhedged or unable to hedge," Mr O'Leary said.
Ryanair shares fell as much as 6%, before eventually closing down nearly 5%, after the airline reported a 29% drop in annual after-tax profit to €1.02bn.
That figure fell within the company's guidance range.
However, it was at the lower end of guidance and Ryanair had already lowered its 2018/'19 profit target twice since last October.
Revenue for the 12 months to the end of March rose 6% to €7.6bn, strongly helped by a 19% jump in ancillary revenues.
Ryanair's average air fares fell 6% during the year, but group passenger numbers grew 9% to 142 million people.
Ryanair's share price has dropped more than 33% in the past 12 months; about 10 percentage points more than that of Aer Lingus-owner IAG and nearly the same amount less than UK rival EasyJet.
For its current year, Ryanair is guiding "broadly flat" group profits of between €750m and €950m.
It said first half bookings are "slightly ahead" year-on-year, but fares are lower.
It said it has zero visibility for the second half of its current financial year and expects its costs this year to increase as its fuel bill jumps by another €460m.
Davy said it will lower its 2019/2020 profit guidance for Ryanair by around 9% to approximately €890m, but suggested Ryanair has hit its nadir with its latest annual performance.
Ryanair has also expressed confidence that a grounding of Boeing's controversial 737-Max aircraft will be lifted in North America in June or July and in Europe around August.
Regulators meet in Texas this week to determine whether the aircraft - involved in two fatal crashes last October and in March - will return.
The meeting comes amid new revelations about problems relating to software used to train pilots of the aircraft.
Mr O'Leary said the disruption had been an "inconvenience" to Ryanair, meaning the airline carried around one million passengers less than planned.
Ryanair has 200 737-Max aircraft on order; 44 of which are due for delivery next winter. The airline has delayed the delivery of the first five to October or November.
"We continue to have utmost confidence in these aircraft which have 4% more seats, are 16% more fuel efficient and generate 40% lower noise emissions," Mr O'Leary said, adding that use of the 737-Max will deliver "significant unit cost savings for the next five years".
Ryanair's board has also approved a €700m share buyback programme, due to commence this week and to run over the next 9-12 months.
It will bring to almost €7bn the amount returned to shareholders since 2008.