The high cost of aviation fuel attributed to the United States and Israel's war against Iran has hit demand for international travel, shrinking passenger numbers at London's Heathrow Airport by more than 5 percent last month.

The sharp fall in demand at Europe's busiest airport meant 6.7 million people used the hub's four terminals during April, compared to 7.1 million during April 2025.

The airport said the change was due to "short-term adjustments to travel plans" because of the "ongoing impact of the Middle East conflict".

The decline in passenger numbers came as Turkiye's fast-growing Istanbul Airport looks set to replace Heathrow as Europe's busiest hub in the coming months.

Experts said Heathrow is seeing both negative and positive impacts from the war. While many people have canceled travel plans because of the high price of fuel and uncertainty, others have been rerouted through Heathrow because of disruption at hubs in the Gulf region, including at airports in Dubai and Doha. Heathrow said those unexpected transfers were up by 10 percent last month.

Heathrow Airport's chief executive, Thomas Woldbye, insisted demand "remains strong" and that fuel supplies are "stable", in spite of shortages because of the blockade of tankers transiting the Strait of Hormuz.

"We know passengers want certainty when planning their hard-earned summer holidays, so we are supporting government and airlines as they work through their plans to get passengers on their journeys," Woldbye added.

Jet fuel was selling for around $180 a barrel in the final week of April, after having been less than half that price a year earlier, the International Air Transport Association has reported.

City AM quoted Tony Fernandes, chief executive of Air Asia, as saying: "I thought I'd seen it all with COVID … but having seen jet fuel go up almost three times — this is much worse."

The high cost of fuel is likely to drive up the cost of travel and could lead to canceled flights, industry experts have warned. And airlines have said the situation could mean operators are forced out of business.

Last week, Spirit Airlines, a US-based low-cost airline, collapsed amid pressure from surging oil prices.

In the UK, the travel industry is one of many sectors being badly damaged by the war in Iran, with the ITEM Club's latest regional outlook predicting the nation could lose 163,000 jobs this year because of the conflict.

The UK-based economic forecasting group said lower-income regions, including South Wales and the area around the River Humber, will bear the brunt of the economic fallout because of their reliance on the manufacturing and construction sectors, which are likely to be hard hit by sharp increases in energy prices and by supply chain disruptions.