Travellers flying to and from Europe this autumn may face lengthy delays as security liquid limits are reinstated at aviation hubs.

Liquids, aerosols and gels (LAGs), as well as pastes, lotions and cosmetics, must be 100ml at all EU airports from 1 September 2024.

The European Commission announced it will “temporarily” reintroduce the restriction on liquids carried in hand luggage on 31 July.

No container for any LAG can be above 100ml, and at most airports must be carried within a resealable clear plastic bag with a maximum volume of one litre.

Europe’s branch of Airports Council International (ACI) predicts that the move will result in “significant operational strain” and “the deployment of additional staff”.

Explosive Detection Systems for Cabin Baggage (EDSCB) operate at several European airports and currently allow passengers to carry liquid containers exceeding 100ml.

Although the advanced CT scanners were installed to enhance airport security and liquids and laptops can stay in a traveller’s bag, the reintroduced restriction could hold up an average of 500,000 people passing through airport security every hour.

The liquids rules were initially introduced in 2006 as “a temporary measure” to protect against explosives after a “liquid bomb plot” on a transatlantic flight.

Olivier Jankovec, ACI Europe director general, said: “Security is non-negotiable, it is at the very top of priorities for Europe’s airports. As such all airports will comply in full with the new restriction. However, the fact remains that those airports which have been early adopters of this new technology are being heavily penalised both operationally and financially.

“They had taken the decision to invest and deploy C3 scanners in good faith, based on the EU having greenlighted this equipment without any restriction attached.”

ACI Europe added that it “regrets” that there is no timeline to reverse the restrictions and called on the European Commission and Member States to “urgently develop a roadmap”.

As for UK airports, from 9 June 2024, the old 100ml rule was reinstated after temporarily being removed, however, passengers can still leave liquids in their cabin baggage at airports that met the deadline to install the new scanners.

The high rejection rate at security after the U-turn caused three-hour long queues at several aviation hubs including Birmingham in June.

A Department for Transport spokesperson said: “The temporary reintroduction of the 100ml liquid restriction at some airports is to allow time to further improve systems.

“It only affects those travelling from six regional airports where next-generation security checkpoints (NGSC) were already in full operation – around 6 per cent of all UK air passengers.”

For more travel news and advice, listen to Simon Calder’s podcast.