The Irish no-frills carrier said fares may drop by 6% over the current quarter compared to an expected 4% as bookings weakened immediately following the atrocity.
Fares were 1% lower in the three months to December, though earnings doubled as the load factor rose by five percentage points to 93%.
Revenue over the quarter was 17% higher at €1.33bn, while profits came in at €103mln (€49mln).
Traffic rose by 20% and Ryanair expects a 26% rise in the current quarter.
Michael O’Leary, chief executive, said strong traffic growth, strong capacity growth but weaker pricing and weaker fares will be drivers over the next six months.
The airline added it was comfortable with full year guidance for net profits towards the upper end of the €1.175bn to €1,225bn range.
The additional profits also mean it can carry out a further €800mln share buy-back programme from February to make it more than €4bn returned since 2008.