Some airports in Spain have spent millions in recent months on new high-tech scanners allowing people to forego the liquid limits that have existed for years for security purposes. However, earlier this month, the European Commission (EC) announced the reintroduction of these regulations at airports across the continent, albeit for a limited amount of time.

As of September 1, some EU airports will bring back the limit on the amount of liquid one vessel can carry and travel experts fear it could cause significant delays.

The "temporary" measure means liquids, aerosols and gels, pastes, lotions and cosmetics can only be carried in the hand luggage if they are in containers not exceeding 100ml each. 

In a press release, the EC said: “The European Commission will temporarily enforce restrictions on liquid screening at EU airports utilising Explosive Detection Systems for Cabin Baggage (EDSCB). 

“These systems, installed in certain EU airports, currently allow passengers to carry liquid containers exceeding 100ml.”

According to the Airports Council International (ACI), the new rule could cause “significant operational strain” and “the deployment of additional staff”.

Although the EC said the measure is temporary, as it stands there is no timeline for its reversal.

Olivier Jankovec, ACI Europe director general, said, as reported by the Independent: "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."

He added: "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."

The reason the rule is being brought back in is "precautionary", as there are some technical issues with the scanning machines. 

The move has not been prompted by increased security threats.