British holidaymakers should arrive at European airports three hours before their flight home departs due to lengthy queues caused by new border checks, the UK boss of budget airline Wizz Air has warned.
Yvonne Moynihan told the BBC the long delays getting through passport control at some European airports had caused some passengers to miss return or connecting flights.
Airports said queues were worsening under the Entry Exit System (EES) which requires travellers to register fingerprints.
But a European Commission spokesperson said EES was working well at "almost all border crossing points".
The EES requires travellers from outside the EU to register biometric information when entering many European countries, which is then checked when they leave.
Since October, almost 80 million entries and exits have been registered, with 35,000 refusals of entry recorded.
From 10 April, it is meant to be fully in use at borders of the Schengen free movement zone, including airports.
However, Greece has effectively suspended biometric checks at its borders for British citizens in order to prevent summer disruption.
Wizz Air's Moynihan said the impact of the new checks was "fragmented across Europe".
While there has been some "seamless travel", she said there had been long queues at "usual hotspots such as Spain, Portugal, France".
When Moynihan travelled to Mallorca for half term, she encountered no queues, with extra staff on hand and "a significant amount of [EES] kiosks".
However, she said in general her airline was advising passengers to prepare for long waits.
"When you land in the destination airport, there might be queues, so you should bring a portable charger or water," she said.
Because EES information has to be verified when people leave, she also highlighted the risk of queues before flights back to the UK.
"Because there is another passport check...that's where we see that people have, again, experienced longer waiting times than anticipated," she said.
She said usual advice is to get to the airport two hours ahead of your flight - "but in these circumstances, we are advising three hours".
Moynihan advised anyone taking a connecting flight to allow "a number of hours" between flights in case of border queues.
She said border officials were proactively suspending EES checks if long waits built up.
The European Commission says EES isn't the only thing that can cause delays, and registering information usually only takes around a minute.
ACI Europe, a trade body for airports, said it surveyed 45 airports in 20 EU states earlier this week.
The results suggested EES was now causing queues of up to three and a half hours.
The group said more airports were now reporting excessive waiting times, despite the "extensive use of partial suspension of EES".
It expected the situation "to deteriorate further" and "become unmanageable" as passenger volumes increased towards the summer peak.
ACI Europe wants any technical issues such as "instability of the central IT system and national interfaces" addressed, as well as border staffing levels.
The Commission said it was up to member states to ensure EES was properly implemented, and they should provide enough border guards.
Portugal, where very long waits have been reported, has announced 360 more border officers for airports in July.
Wizz Air's Moynihan acknowledged improvements had been made after initial teething issues and glitches.
But she thought the higher number of people travelling over summer would test the system, and called for more countries to suspend the checks over the peak period.
The European Commission told the BBC that until September it was allowing biometric registration to be suspended "at specific border crossing points and for a limited amount of time in cases of exceptional circumstances that lead to excessive waiting times".
With the summer holidays approaching, there has been speculation that the situation in the Middle East could spark jet fuel supply issues and cancellations.
Like other airlines, Wizz has seen a trend of late bookings.
This has led to "very affordable prices" to stimulate demand.
But Moynihan also insisted passengers "should feel confident booking", echoing the words of other short-haul airline bosses such as EasyJet and Jet2.
However, the Wizz Air UK boss insisted its suppliers had adapted, no shortages were anticipated, and no cuts to its schedule were expected.
Fares are likely to go up in the future if oil prices remain high. However, Moynihan said in the short term, carriers like hers could save costs in other areas.
