The head of Europe's airports trade body says concerns over the region's new digital border control system are keeping him and other industry bosses awake at night.

Earlier this year, the EU completed the rollout of its Entry-Exit System (EES). It requires travellers from outside the EU to register biometric information when entering most European countries, which is then checked when they leave.

Although EES has been working well in some countries, it has also been blamed for causing significant delays at a number of airports, with some passengers missing flights.

Stefan Schulte, president of ACI Europe, said politicians should "stop pretending... that EES is working just fine. It is not."

Schulte, who is also head of the company that owns Frankfurt Airport, told an industry event in Prague: "Passengers are queueing for hours at peak traffic times and I just do not know how we will be able to cope in the coming weeks with the expected increase in traffic."

The BBC has contacted the European Commission, which oversees the EES, for comment.

Ryanair blamed border delays, while the airport said it had been experiencing congestion linked to "additional processing requirements", though neither directly said EES was responsible.

However, it marked the latest incident of passengers being left behind since EES was brought in. In April, some passengers due to fly from Milan Bergamo and Milan Linate to Manchester also missed their flights due to problems at passport control.

The system obliges most travellers from outside the European Economic Area to register biometric data, including facial scans and fingerprints, which can then be checked each time they cross the borders of the Schengen free travel zone.

Wizz Air has previously urged British holidaymakers to arrive at European airports three hours before their flight home departs due to lengthy queues caused by the new border checks.

"We urgently need full flexibility for border control authorities to suspend the EES whenever needed to avoid further chaos – along with a rethink of those processes," Schulte said.

"This is about showing respect and decency for those who chose to travel to the EU, and safeguarding our reputation as a welcoming and efficient destination."

The European Commission is allowing EES to be suspended in some circumstances until September.

But Schulte told the BBC's World at One programme that individual governments had to make the decision to suspend the system, not airports themselves, adding that queues lengthened while such decisions were being made.

He also warned that the summer peak lasts much longer than early September and after that, we were potentially looking at the "complete collapse of the system".

Earlier this year Greece's tourism minister said she did not want visitors to be "burdened" by bureaucratic procedures when entering or leaving the country.

Olga Kefalogianni promised British passengers would not face biometric checks when travelling to Greece this summer.

But the situation remains unclear after the Greek Foreign Ministry later disputed that any exemption existed.

There were also reports that Portugal and Italy were considering exempting British nationals from EES checks at their airports, but the European Commission claimed there were no such plans in place.