He added that the low-cost carrier, Europe's largest airline by passenger numbers, has engaged in almost no price discounting since September, with the exception of a modest Black Friday sale, owing to the strength in demand since the summer. Earlier this week, he had said that the winter for Ryanair was "amazing".

Separately, Wizz Air boss Jozsef Varadi told a conference in Gibraltar that bookings at Wizz Air were intact for the next three months. 

Shares in Ryanair have risen sharply, by over 10%, in the past month as the prospects for airline bookings have improved despite increased fuel costs and the cost-of-living crisis across Europe. Its shares are, however, still down 20% from a year ago, to value the carrier at just over €15bn. 

Wizz Air shares have soared 30% in the past month but are still 45% down from a year ago. It is valued at almost €2.3bn.                                   

Meanwhile, Ryanair said it has signed a sustainable aviation fuel-supply agreement with Shell, but Mr O'Leary said it would take a "revolution" to hit his target of powering 12.5% of flights with the fuel by 2030.

The airline said the memorandum of understanding could give it potential access to 360,000 tonnes of sustainable fuel from 2025 to 2030, a fifth of what it says it needs to reach its 12.5% target.

"I'm not sure we'll get there but by signing up more partnership agreements with Shell, with Neste and with the other fuel suppliers, I think that gives us our best chance of maybe getting to 8, maybe 10, maybe 11," O'Leary told a sustainability conference in Dublin that the airline was hosting. 

Dramatic revolution

"Who knows, hopefully we will get to 12.5% by 2030. But that will not happen unless we have a dramatic revolution in supply of production of SAFs [sustainable aviation fuels] and availability at our airports," he said. 

The Shell deal follows similar agreements Ryanair has struck with Finnish biofuel producer Neste and Austrian oil and gas group OMV. 

Sustainable jet fuel generally produces up to 70% less carbon than fossil fuels, offering airlines a way to become greener while continuing to fly, before less carbon-intensive hybrid, electric, or hydrogen aeroplane options become available.

Mr O'Leary had told the Oireachtas Transport Committee earlier this week that he did not expect a hydrogen engine to be ready before 2040 or 2050.

Ryanair has committed to cutting its carbon emissions to net zero by 2050 and said the Shell agreement could save 900,000 tonnes in carbon dioxide emissions, equivalent to more than 70,000 flights from Dublin to Milan.

Ryanair operates an average of 3,000 flights per day and plans to grow from a record 168m passengers this financial year to 225m by 2026.

Shell aims for renewable fuel to account for 10% of its global jet sales by 2030. 

• Reuters. Additional reporting by Irish Examiner