Drivers have been told to expect the UK’s busiest May bank holiday traffic in years, despite high fuel prices and the looming end of the sunny spell threatening to dampen the long weekend.

More than 19m leisure trips by car were expected over the long weekend from Friday to Monday, according to research by the RAC motoring organisation – the most since 2016. Engineering works are also likely to disrupt rail journeys this weekend.

Almost 40% of drivers surveyed were planning an overnight break or day trip, with only 6% saying they were deterred by the surge in pump prices since the start of the hostilities in the Middle East.

Friday will see early getaways meeting commuter traffic and school runs, although the RAC has pinpointed late Saturday morning as the peak time for cars on the roads.

It highlighted the M5 from Bristol to Taunton as a likely congestion black spot as drivers head to Devon and Cornwall – although the traditional bank holiday change in weather to heavy rain, after a week of sunshine over much of the UK, could now see many plans change.

Meanwhile, engineering works on the railway will mean longer journeys and replacement buses for passengers around the country, including on the mainline from London to Edinburgh, as well as Liverpool and Bath.

Network Rail said the “vast majority” of Britain’s railway network will be open as usual but with “some notable exceptions” for works.

The east coast mainline will be shut between York and Darlington for three days from Saturday, adding hours to journeys between the capital and Edinburgh or Newcastle.

Works on the line running out of London Euston will mean slightly fewer and slower services to cities in the Midlands and the north over the weekend.

Liverpool’s Lime Street station will be closed all day on Sunday and until noon on Monday.

London’s Charing Cross and Waterloo East stations will also be closed for the same period.

Work around Bath Spa, Huddersfield and Ely will also disrupt journeys.

Anit Chandarana, a group director for Network Rail, said: “There is no right way to do major work on our railway, but bank holidays are still among the least busy times for us in terms of passenger numbers and freight services.

“I’d advise everyone to plan ahead and check before they travel.”

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.

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 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.

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.

Nearly 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.

Penalties on airlines that cancel UK flights because of jet fuel shortages have been eased, it has emerged, as the government issued fresh advice to reassure the public they can still fly and should stick to travel plans.

Airlines that cancel owing to 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.

The change was one of the demands from airlines, which have been lobbying for government help in the face of rising fuel prices and a possible supply crisis.

Exemptions from the “use it or lose it” rule can now be granted during shortages by Airport Coordination Limited, the independent body that manages slots at UK airports. The government said the change would allow carriers to “focus on minimising disruption” rather than flying to protect slots.

Despite the move, the government said there was “no current need for passengers to change their travel plans”, in online advice published by the Department for Transport on Friday.

It said that UK airlines were “clear that they are not currently seeing a shortage of jet fuel” and that the government was regularly meeting with the industry to monitor the risks.

It added: “We recognise that families may be concerned, and that aviation and tourism businesses are operating in challenging global conditions. We are working hand in hand with industry to help flights keep operating.”

However, it also advised passengers to “continue checking with their airlines before they travel”, as well as having insurance.

It stressed that passengers have the right to a full refund or to an alternative flight to the destination if a service is cancelled.

But airlines have also lobbied to have fuel shortages count as an exceptional circumstance that would exempt them from paying any additional compensation should they cancel flights with less than 14 days’ notice.

While some European carriers have already cut back schedules – notably Lufthansa, which this week cancelled 20,000 summer flights – UK airlines have largely taken pains to promote business as usual, in the face of consumer anxiety about costs and cancellations.

The tour operator Jet2 on Friday said it would not add any fuel surcharge to flights or holidays booked this summer. Steve Heapy, the chief executive, said: “Holidaymakers should have every right to book their hard-earned break in the sun without worrying about being hit with additional costs, and they can have that complete assurance when they book a flight or holiday with Jet2.”