Britis are being warned to brace for a difficult summer of travel disruption. Experts are warning travellers that they could be hit with queues of up to four hours. Alongside fuel concerns, passengers are also facing delays caused by the rollout of new EU border controls. The European Union's new Entry/Exit System (EES) launched last Friday, on April 10, and has led to long queues at passport control across the continent.

The system applies to all passengers from countries outside the EU and Schengen area who are entering the 29 participating countries for short-term stays. UK travellers are therefore now required to scan their passports and provide biometric data, including facial scans and fingerprints, instead of the previous passport stamping.

The system monitors how long visitors remain to guarantee they don't surpass the 90-day threshold within 180 days. Once passengers submit their biometric details, those details remain valid for three years.

Early implementation issues, however, have raised fears of bottlenecks at busy airports. Passengers across France, Germany, Belgium, Italy, Spain, Portugal and Greece are waiting hours at passport control, the Airports Council International (ACI) body has said.

Olivier Jankovec, the director of the ACI European division, told the Financial Times: "This situation, in the coming weeks and certainly over the peak summer months, is going to be simply unmanageable.

"We are seeing those queueing times now, at peak times, when traffic is just starting to build up."

According to the ACI, processing times have increased by up to 70% in some locations due to additional steps involved in biometric data collection.

Thomas Reynaert, senior vice president, External Affairs, at the International Air Transport Association (IATA), also said: "We are very concerned about the lack of progress in resolving problems with the EES.

"Unless there is action to ensure borders are adequately manned and the electronic gates and remote app are working properly, we could see passengers, including families with kids, queuing up to four hours in popular holiday destinations."

Passengers reported queues of up to three hours at Milan's Linate airport on Sunday. Over 100 passengers missed an easyJet flight from Milan to Manchester with only 34 of 156 passengers boarding on time.

As well as concerns over how to return home, many passengers were left vomiting and passing out due to the heat, according to the BBC.

Many passengers are also reportedly facing waits of up to three hours at Spanish airports due to the new controls.