Holidaymakers will continue to face limits on the amount of liquid they can carry on flights out of the UK this summer after the government extended the deadline for airports to install new security scanners by a year.

The Department for Transport had previously set a target for the introduction of 3D scanners in all UK airports by 1 June, but this has now been extended by 12 months because some major airports will not be ready in time.

Heathrow, Gatwick and Manchester Airports Group, which owns Manchester airport and Stansted, said in January that they would not meet the deadline and hoped the latest scanners would be fully operational in 2025.

The scanners, which have already been fully introduced at London City airport and Teesside airport, use computed tomography to produce clearer and more accurate images.

They also include the latest explosive detection capabilities, which can detect threats without the need for liquid containers to be removed.

When introduced, the current 100ml limit on the amount of liquid that can be held in carry-on luggage will be scrapped and replaced with a two-litre rule.

Nor will liquids and laptops have to be removed from carry-on bags, speeding up the security process.

The restrictions on liquids were introduced in 2006 after security officials foiled a plan to blow up a transatlantic flight using liquid concealed in a bottle of soft drink.

The government is now telling travellers that they should continue to expect the current 100ml rule throughout the summer.

Th aviation minister, Anthony Browne, said: “By 1 June, more than 50% of passengers will be going through the new security checkpoint, but our message is that travellers should prepare for the current rules to be in place and check what the specific rules are for the airport they are using.”

Department for Transport officials said some airports had faced supply-chain delays in securing orders for their scanners.

Other airports had been hit with construction problems, including having to reinforce floors because of the weight of the machines.

The government said it would issue penalties for airports that were not ready after the June 2025 deadline, but gave no details of what they might be.

It is the second time the government has been forced to delay the rollout after initially setting a deadline of 2022.

The installation of the new scanners has come with additional costs for airports. Heathrow is spending about £1bn on the new equipment, including upgrading 146 security lanes across four terminals. The Guardian has contacted Heathrow about its progress.

Manchester Airports Group said it was making good progress at both of its sites and was introducing the upgrades lane-by-lane, with several already operational. Full completion of the programme is expected next year.

Gatwick said its position was unchanged from January when it indicated a completion date of spring 2025.

London Luton airport also has some lanes operational and said it was “making excellent progress” towards the June deadline.

Newcastle airport said it had already installed the technology, and Bristol airport said it would meet the government’s deadline.

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