UK holidaymakers flying home from Europe this weekend are being urged to arrive at airports at least three hours before their flight because of chaos caused by new passport controls.
Queues of up to four hours have been reported since the introduction of more stringent checks on travellers entering and leaving the Schengen area, which allows passport-free movement across much of the EU.
Airports in Spain, Portugal, France, Italy and Belgium have been affected.
The situation could worsen this weekend as lobby group Airlines For Europewarned it will be one of the busiest of the year with 10 million people expected to pass through European airports on Saturday and Sunday combined.
Some airports, such as Majorca, are predicted to experience double their usual demand.
British Airways, easyJet and Ryanair have all alerted passengers to the need to turn up at airports earlier than normal.
Ryanair issued an alert which urged its customers to arrive "at least three hours before the scheduled departure time".
BA is sending text messages to passengers flying back from airports where long lines at border controls are expected.
The carrier has promised that any customers who miss their flight because of the queues will be re-booked for free.
The extra security measures were brought in following terror attacks in Paris and Brussels.
They have led to long lines at border controls as the details of passengers from non-Schengen countries - such as the UK - are run through databases to alert authorities if they are known to pose a threat.
Ryanair boss Michael O'Leary said earlier this week that more than a fifth of the airline's flights were being delayed because of the issue and he is "jumping up and down" in frustration.
Just 78 per cent of the Dublin-based carrier's flights were on time on Tuesday, down from 90 per cent during the month of August as a whole last year.
European Commission spokeswoman Mina Andreeva said there was a "price to be paid" for security, but insisted that EU countries should have put arrangements in place to avoid lengthy queues.
