British refineries have been asked to maximise jet fuel supply as part of government contingency planning, amid growing fears the Iran war will force planes to be grounded.

The energy minister Michael Shanks said the government is closely monitoring UK jet fuel stocks and working with airlines, airports, fuel suppliers and other governments, as carriers face rocketing fuel costs as a result of the conflict.

Normal flows of fossil fuels from the Gulf have effectively been at a standstill since the war broke out, after the de facto closure of the important shipping channel, the strait of Hormuz, through which a fifth of the world’s oil and gas flows.

“UK airlines typically buy fuel months in advance, and aviation fuel suppliers hold bunkered stocks. The UK imports jet fuel supplies from a range of countries not reliant on the strait, including the United States,” wrote Shanks in a ministerial statement.

“Airlines UK have stated that ‘UK airlines continue to operate normally and are not experiencing issues with jet fuel supply.’ The government continues to work with partners to monitor and mitigate potential disruptions,” Shanks added.

There are now only four remaining refineries in the UK, after closures at the Grangemouth and Lindsey refineries in 2025.

The remaining UK refineries are: Fawley in Hampshire owned by ExxonMobil; Humber in Lincolnshire owned by Phillips 66; Valero’s Pembroke refinery in Wales; and Essar’s Stanlow site in Essex.

These sites produce a range of refined products including petrol, diesel, jet fuel and fuel oil to meet domestic demand and for export. The number of UK refineries has fallen from a peak of 18 in the 1970s, as has the UK’s output of petrol and diesel.

It came as global jet fuel shipments fell to the lowest recorded level last week. Just under 2.3m tonnes of jet fuel and kerosene were transported on ships in the seven days to 26 April, according to initial analysis by the data company Kpler, which first began tracking shipments in 2017. The figure represents less than half the average weekly volume shipped before the war.

Airlines have insisted there are now no supply problems expected during their typical four-to-six-week horizon, although some carriers have already announced flight cancellations and have been lobbying for government help amid rising fuel prices and a possible supply crisis.

Airlines that cancel flights because of a lack of fuel will not lose their rights to valuable takeoff and landing slots at busy airports, which can be forfeited when flights fail to operate over a period.

It was announced on Friday that exemptions to the “use-it-or-lose-it” rule can be granted during shortages by Airport Coordination Ltd, the independent body that manages slots at UK airports, in an attempt to minimise disruption and prevent airlines from flying to protect slots.

The budget travel carrier Jet2 said on Wednesday it remained in contact with its fuel suppliers and airports.

The group said it had hedged 87% of its fuel requirement for the peak summer season, at an average price of $707 a metric tonne, giving it “a high degree of cost certainty”.

Jet2 said “current geopolitical uncertainty” over the Middle East conflict meant holidaymakers were booking trips closer to departure, making it difficult to predict bookings for the peak summer season and beyond.

Heathrow airport also told investors it was facing an “uncertain outlook” as a result of the conflict despite reporting a short-term boost in the number of passengers travelling through the airport to change planes because of airspace closures in the Middle East.

Almost 19 million passengers travelled through the airport during the first three months of the year, an increase of 3.7% compared with a year earlier.

Heathrow said it had “temporarily absorbed demand from elsewhere” but did not expect this to continue for the rest of the year, given “significant uncertainty” in the region.