In an interview with the Financial Times, the boss of the no frills carrier said flying had become too cheap to be sustainable in the medium term.

Air fares across Europe have already risen due to low capacity and high demand this summer, and O’Leary warns this trend is set to continue. Data from Kayak.com reveals fares to European holiday hotspots such as Greece and Spain have jumped in the last year.

“Ultimately, I don’t believe air travel is sustainable over the medium term at an average fare of €40," O’Leary told the paper. "It’s too cheap at that. I find it absurd every time that I fly to Stansted, the train journey into central London is more expensive than the air fare."

The average one-way Ryanair fare could go up from €40 to between €50 and €60, according to O’Leary, who was a pioneer of cheap air travel when he transformed Ryanair into Europe’s biggest airline in the 1990s.

He said oil prices will remain high, putting pressure on airlines to hike fares “until we can wean ourselves off Russian oil”. Environmental charges requiring airlines to buy credits to offset carbon emissions in the UK and EU are also contributing to increasing flight prices, said O’Leary.

In the interview, O’Leary blamed the staff shortages at British airports this summer on Brexit, preventing airlines from easily hiring European workers. “This is without doubt one of the inevitable consequences of the disaster that has been Brexit,” he said.

Ryanair is one of the only European airlines not disrupted by staff shortages, and O’Leary says this is down to its decision to keep staff on with reduced pay during the pandemic, while other company’s laid off workers.