The Ryanair CEO has warned there is no "100% guarantee" Europe won't face supply issues from June onwards, as the jet fuel crisis looms.

Fuel costs increased and more than doubled since the start of the war in Iran in February and many airlines around the world have reduced the number of their flights or increased prices.

Rynair's chief Michael O'Leary, speaking to POLITICO, said the situation is "modestly improving at the moment," but could not rule out supply issues in the near future. O'Leary said: “Our suppliers, which are all the major oil companies, are saying, ‘We don't see any significant issues until about early June.'”

According to O'Leary, the pressure eased thanks to jet fuel coming from West Africa, the US, and Normay. He also mentioned an increasing supply coming from Russia.

But “nobody is telling us there's a 100 percent guarantee out into June, July and August,” he also warned. He also added that some European airlines could go bankrupt if they cannot deal with the soaring costs. “A number of our not-so-low-cost competitors will fail in the autumn,” he said.

Speaking to POLITICO he also said that Ryanair was somewhat insulated from the price surge because it has hedged about 80 percent of its fuel needs at the pre-war price of $67 a barrel, while the remaining 20 percent must be purchased at around $150 a barrel.

Fatih Birol, the head of the International Energy Agency (IEA) warned this month that Europe has “maybe six weeks” of jet fuel left, and if oil supplies remain restricted by the Iran war, it could result in cancelled holidays.

In response to the warnings, the FCDO has stressed that there is “no current need” for passengers to change their travel plans for this summer. UK airlines said they are not currently seeing a shortage of jet fuel as it is typically bought in advance, with airports and their suppliers keeping stocked of bunkered fuel to support their resilience.

The energy crisis, however, has already prompted some airlines to raise ticket prices or add fuel surcharges, with both KLM and Lufthansa reducing their flight schedules due to rising fuel costs.

Lufthansa has also announced the immediate closure of its feeder airline CityLine, taking 27 older aircraft out of service early, Scandinavian carrier SAS has cancelled at least a thousand flights in April, and easyJet has taken a £25 million hit on surging fuel prices.