Irish and British people flying to and from Europe for their summer holidays face the prospect of "devastating" delays due to stricter Schengen area border controls, Europe's largest airline lobby group has warned.
Explainer: 'Crazy' airport delays across Europe - why are there suddenly queues?
Thousands travelling from Spain, Portugal, France and Italy have been hit by lengthy airport queues, with some missing flights over new passport controls - writes Irish Independent
So, what's different this summer? We've answered all your questions here.
What's changed this summer?
A new European regulation came into effect on April 7, 2017 that requires every passport to be checked when arriving and leaving the "Schengen area" - that's the "frontier-free" zone comprising most EU countries plus Switzerland, Norway, Iceland and Liechtenstein, but excluding the UK and Ireland.
Before then, Irish and British holidaymakers found border control in Spain and other European countries very easy.
Now though, every passenger's passport is electronically compared against the "Schengen Information System", a big pan-European database - and also against Interpol's list of stolen and lost travel documents due to recent terror attacks. As a result, the processing time has gone from a couple of minutes to what could be several hours. It's only now, at the peak of the summer season, that the most extreme effects are becoming clear.
What are the new procedures when you're flying out of the Schengen area?
The standard search for weapons, explosives and liquids over 100ml has not changed. But once you get through into the departures area there are long queues from the passport desks for travellers heading out of the Schengen area.
It's a simple matter of resources; it appears there aren't enough people or electronic checkpoints to cope with the demands of the new rules at peak times.
Which airports are affected?
According to the group Airlines for Europe the airports of Palma, Barcelona, Alicante or Malaga in Spain are seeing waits of up to four hours.
The organisation also warns of long queues at Madrid, Lisbon, Lyon, Paris-Orly, Milan and Brussels, but since these are primarily business hubs they are not as badly affected as key holiday airports.
Passengers can arrive many hours early, but often check-in opens only two hours before departure. Therefore being at the head of the queue is a good idea.
Will airlines wait for passengers who are held up in queues?
In some circumstances, they might. If you have booked a package holiday through a travel agency, with accommodation and transfers as well as flights, they should arrange the coach journey back to the airport to come home with plenty of time to spare.
Do I get compensation if I miss my flight home?
No, the opposite applies: you are likely to have a stressful time. If you miss a plane because you failed to comply with the airline's stipulation about when to reach the gate, you'll have to buy a new flight.
And with planes flying fuller than ever before, finding another seat will be difficult and expensive.
Have many flights been delayed?
Aage Duenhaupt, a spokesman for A4E, which represents airlines including BA's owner, International Airlines Group, Ryanair and easyJet, said thousands of flights had already been delayed because of tighter checks at some EU airports.
Mr Duenhaupt said the bank holiday weekend, which is one of the busiest times of the year, could see delays of up to two hours. He noted that for example there were 200,000 passengers arriving in and departing from the Spanish island of Mallorca.
"Unless Spanish border control puts in place an emergency plan to avoid queues and help passengers to get through faster, there will be a lot of devastating delays for passengers," he said. "It's a crazy situation."
What are airlines and travel reps saying?
Ryanair is now asking its passengers to check in three hours before departure.
Meanwhile, travel agent reps are seeking talks with the Department of Justice over what they claim are "staffing shortages" in Irish airports, causing delays. President of the Irish Travel Agents Association (ITAA) Cormac Meehan said a lack of passport control lines which are open for those travellers coming into the country, among other things, are causing problems on the other side.
Mr Meehan said Terminal One and Terminal Two in Dublin Airport are a particular problem with large queues. He explained the feedback received from customers was there were not enough staff on duty to get them through the passport control. "The ITAA has called for a meeting with the Department of Justice and Equality to get the issue of understaffing at Dublin Airport and other regional and national airports on to the national agenda, given the importance of the sector to the national economy," Mr Meehan said.
"Not enough of them are operational."
However, the Dublin Airport Authority (DAA) has insisted there are no delays from its security screening section. A spokesperson said it is usually a 15-minute process going out of the country.
Any tips for Irish people travelling abroad?
For Irish holidaymakers travelling back into the country, new rules mean name checks against a series of databases are now carried out for those outside of the Schengen border-free area. Mr Meehan said those travelling abroad from Ireland should take out adequate travel insurance and ensure they arrive at airports three hours before their flight.
Meanwhile, a security expert has backed the more stringent security measures implemented across Europe. Tom Clonan said while it's "frustrating and inconvenient, it's necessary".
"People are just going to have to incorporate that into their planning. Islamist extremists have targeted airports in the past. I would prefer to queue for four hours and fly safely. It's better to be safe than sorry."
Read more news of Dublin here.