By bizn_fun 
Olivier Jankovec is director general of Airports Council International Europe, which represents more than 600 airports.
He told the BBC the passenger processing time at border control had increased by “four to five times” under EES, with people typically waiting up to two hours.
Jankovec said problems included not enough border staff, and some machines not working.
He fears the situation will worsen when large numbers of holidaymakers register over Easter and summer.
Markus Lammert, European Commission Spokesperson for Internal Affairs, says 23m entries and exits have already been registered under EES, and there have been 12,000 refusals of entry.
He insisted the system has operated “largely without issues”, but said member states would continue to work on improvements.
From 10 April, EES is meant to be in use at every border point, for every eligible passenger.
However, countries can partially suspend EES operations where necessary over the summer, until September.
Jankovec said this would be necessary to cope if “the situation becomes unsustainable at border control”.
Without it, and if issues around the equipment and border guard numbers didn’t improve, he warned of five-to-six-hour waiting times.
The group said close coordination was needed with border control authorities to make sure they could suspend the system “in a timely manner”.
On Thursday, travel association ABTA said border authorities were under-using their ability to reduce checks when necessary, and said this had led to passengers being “caught up in lengthy delays”.
ABTA said that as well applying the contingency measures, destinations and border authorities need to do more to plan for peak travel periods.
Julia Lo Bue-Said advised people to come prepared for long waits over the February half term and beyond.
“Plan for the worst”, she advises, especially at peak times. “Make sure you’ve got some refreshments, make sure you’ve got something to keep [small children] occupied”.