Oil prices climbed sharply on Monday after Iran reversed a brief decision to reopen the Strait of Hormuz, the narrow waterway between the Persian Gulf and the Gulf of Oman through which roughly 20% of the world's oil exports pass. US benchmark crude rose 5.6% to $87.20 a barrel, while Brent crude — the international standard — gained 5.3% to $95.16, erasing much of the relief that had briefly lifted global markets when Iran's foreign minister announced the strait was open. That optimism quickly faded after President Donald Trump confirmed a US Navy blockade of Iranian ports remained "in full force," and Iran's military vowed to respond to the US seizure of an Iranian-flagged cargo ship it accused of attempting to breach the blockade. A fragile two-week ceasefire between the US and Iran is set to expire on Wednesday, with Tehran signalling it will not participate in a second round of negotiations.

For Europe, the crisis carries consequences that go well beyond fuel prices at the pump. The continent is unusually exposed: it depends on the Middle East for roughly 75% of its aviation fuel net imports. The International Energy Agency estimates that OECD Europe requires around 1.6 million barrels of jet fuel per day, of which approximately 375,000 barrels typically arrive from the Middle East. Since the conflict disrupted shipping in late February, European jet fuel prices have nearly doubled — from $831 per tonne before the war to a record $1,900 per tonne by early April. Suppliers have reportedly stopped offering forecasts beyond a single month, an uncertainty that itself constitutes a serious operational disruption.

The effects are already cascading through the industry. Four major Italian airports — Milan Linate, Bologna, Venice, and Treviso — began rationing jet fuel on 6 April, prioritising medical flights, government aircraft, and routes longer than three hours. Short-haul flights are capped at 2,000 litres per aircraft, barely enough to fly a single-aisle jet like a Boeing 737 or Airbus A320 for about an hour. Lufthansa has retired 27 regional aircraft ahead of schedule, citing fuel efficiency concerns. SAS is cancelling more than a thousand flights in April, Ryanair's chief executive has warned of further summer capacity cuts, and Wizz Air projects a €50 million hit to annual profits. The International Air Transport Association's director general, Willie Walsh, has called on authorities to move beyond monitoring and begin coordinating contingency rationing plans before May, when he warns cancellations due to fuel shortages could begin in earnest.

The picture across Europe is uneven. Spain, which has eight refineries and meets roughly 80% of its jet fuel needs domestically, is among the most insulated. The United Kingdom, which imports more than 60% of its aviation fuel, is among the most vulnerable. France currently sits in a relatively stable position — Paris airports are supplied via a dedicated pipeline from Le Havre — though Air France has raised long-haul fuel surcharges by up to €100 per return ticket. The EU Commission has acknowledged the market is "tight" while stopping short of declaring a shortage, describing rationing at individual airports as local decisions. Behind the scenes, however, the EU's energy commissioner has written to member states urging energy-saving measures in the transport sector, and a full package of aviation-specific measures is expected to be announced imminently, following an emergency meeting of EU transport ministers.

The crisis has also exposed a structural vulnerability in Europe's energy transition. The continent has reduced its active refineries from 117 to 96 since 2009, and the IEA notes that remaining facilities are already operating near capacity for jet fuel production. Sustainable aviation fuel, intended as a long-term alternative, cannot bridge the gap in the short term — and 69% of Europe's SAF feedstock is itself imported, with more than 30% coming from China. The IEA's executive director, Fatih Birol, has warned that even if a ceasefire or peace deal were reached, damaged energy infrastructure in the Middle East would take time to restore. The worst-case scenario of mass groundings remains unlikely, but a slow, uneven erosion of connectivity — hitting smaller airports, thinner routes, and less profitable markets first — is already under way. Airlines in Japan have also moved to raise international fuel surcharges ahead of schedule, reflecting how broadly the disruption is rippling beyond Europe.