Got European travel plans this summer? Don’t forget to pack your passport, sunscreen and plenty of patience.

Liz Morgan arrived at Amsterdam’s Schiphol Airport 4 1/2 hours before her flight to Athens, finding the line for security snaking out of the terminal and into a big tent along a road before doubling back inside the main building.

“There’s elderly people in the queues, there’s kids, babies. No water, no nothing. No signage, no one helping, no toilets,” said Morgan, who is from Australia and had tried to save time Monday by checking in online and taking only a carry-on bag.

People “couldn’t get to the toilet because if you go out of the queue, you lost your spot,” she said.

After two years of pandemic restrictions, travel demand has roared back, but airlines and airports that slashed jobs during the depths of the COVID-19 crisis are struggling to keep up. With the busy summer tourism season underway in Europe, passengers are encountering chaotic scenes at airports, including lengthy delays, canceled flights and headaches over lost luggage.

Schiphol, the Netherlands’ busiest airport, is trimming flights, saying there are thousands of airline seats per day above the capacity that security staff can handle. Dutch carrier KLM apologized for stranding passengers there this month.

London’s Gatwick and Heathrow airports are asking airlines to cap their flight numbers. Discount carrier easyJet is scrapping thousands of summer flights to avoid last-minute cancellations and in response to caps at Gatwick and Schiphol. North American airlines wrote to Ireland’s transport chief demanding urgent action to tackle “significant delays” at Dublin’s airport.

Nearly 2,000 flights from major continental European airports were cancelled one week this month, with Schiphol accounting for nearly 9%, according to data from aviation consultancy Cirium. A further 376 flights were canceled from U.K. airports, with Heathrow accounting for 28%, Cirium said.

It’s a similar story in the United States, where airlines cancelled thousands of flights over two days last week because of bad weather just as crowds of summer tourists grow.

“In the vast majority of cases, people are traveling,” said Julia Lo Bue-Said, CEO of the Advantage Travel Group, which represents about 350 U.K. travel agents. But airports are suffering from staff shortages, and it’s taking a lot longer to process security clearances for newly hired workers, she said.

“They’re all creating bottlenecks in the system,” and it also means “when things go wrong, that they’re going drastically wrong,” she said.

The Biden administration scrapping COVID-19 tests for people entering the U.S. is giving an extra boost to pent-up demand for transatlantic travel. Bue-Said said travel agents her group represents reported a jump in U.S. bookings after the requirement was dropped this month.

For American travelers to Europe, the dollar strengthening against the euro and the pound is also a factor, because it makes paying for hotels and restaurants more affordable.