The budget airline has hedged its jet fuel costs at US$92 a barrel for 2016 - the current price of a barrel of Brent crude stands at US$50.
Some of its rivals opted against locking in their fuel costs and look set to be able to pass on cheaper fares, meaning price competition will be fierce.
Chief executive Michael O’Leary said Ryanair intends to pass on much, if not all, of these fuel savings to its customer base in the form of lower fares.
He then warned shareholders and analysts to "temper expectations" for full-year profits in 2015-16.
The airline did, however, raise its full-year earnings outlook for the 12 months to 31 March 2015 and said it will buy back €400mln worth of shares after returning to profit in the last three months of 2014.
The low-cost Irish carrier made a net profit of €49mln in the quarter to December compared to a loss of €35mln for the last three months of 2013.
Traffic jumped by 14% to 21mln customers and average fares were up 2% to €40 as revenues increased by 17% to €1.13bn while costs fell 6%.
Looking ahead, the airline said traffic for the three months to 30 March was expected to rise by 25%, while falling oil prices would cut costs by 5%.
It increased guidance for full-year net profits from between €810mln and €830mln to a range of €840mln to €850mln.
The share buy-back programme will start on 12 February and continue until August.
Meanwhile, a €520mln special dividend (€0.375 per share) will be paid to shareholders on 27 February.
Meanwhile, the group holds a 29% stake in Aer Lingus – which is the subject of a €1.4bn takeover bid by British Airways owner IAG.
O’Leary added today that Ryanair had received no formal offer for its holding and that it would "carefully consider" any approach.
Broker Kepler Cheuvreux downgraded the airline from Buy to Hold.
Shares lost 6% to €9.70.