From Dublin, Sao Paolo, Brussels, London and other cities around the world, international visitors spilled into U.S. airports Monday in joyous celebrations that marked the end of a pandemic-related travel ban that kept them separated from loved ones for more than 18 months.

“On behalf of the U.S. travel industry: WELCOME,” the U.S. Travel Association said in a tweet Monday morning. “Today marks a monumental and long-awaited day for travelers, long-separated friends and family who can now safely reunite with loved ones.”

The end of a 33-nation ban that kept most non-U.S. citizens out of the country took on a celebratory air Monday, throwing a lifeline to an industry seeking to rebound from the pandemic. It sparked reunions at international airports across the country, but comes as U.S. airlines — which have seen a surge in demand from domestic leisure travelers — are struggling to overcome staffing shortages ahead of the busy travel holiday season. The United States also lifted travel restrictions on land borders, a move that allows fully vaccinated individuals to enter the country from Canada and Mexico. Previously only those whose travel was deemed essential and could show proof of vaccination could enter the United States via land crossing.

Families were reunited at airports across the country after the United States reopened its borders to fully vaccinated international travelers on Nov. 8. (Reuters)

Earlier this month, American Airlines angered passengers after it canceled nearly 2,000 flights, citing staffing shortages and bad weather at its Dallas-Fort Worth hub. Southwest Airlines reported losing more than $75 million after it was forced to cancel more than 2,000 flights in October.

Scheduling meltdowns that began amid a summer travel boom have left passengers and observers questioning whether the industry is equipped to handle a continuing rise in passenger levels — and the added responsibilities of screening a growing number of international visitors.

Under the new requirements, airlines are responsible for verifying travelers’ vaccination statuses and ensuring negative coronavirus test results for those who are exempt from mandates. Carriers say they are prepared for the new responsibilities, adding that measures they have put into place — including digital tools that allow travelers to upload coronavirus test results and verify vaccinations — will smooth travel for customers. Several international airports also offer on-site testing, making it easier for travelers to meet U.S. testing requirements.

“Today marks a significant milestone in the progress of worldwide recovery from the covid-19 pandemic,” said Nicholas E. Calio, president of airline trade group Airlines for America.

Henry Harteveldt, an industry analyst and co-founder of Atmosphere Research Group, said carriers will be able to handle the growth in international visitors without too much additional strain.

“For one thing, they do have the pilots and flight attendants trained and ready, though granted, they may need to bring more back,” he said. “The airlines are also not over-scheduling their long-haul route networks yet.”

Officials with U.S. Customs and Border Protection, which handles international arrivals, said they were making preparations to handle the rise in visitors and were working to add staffing at key entry points. The agency warned that travelers should expect longer lines this week as those eager to reunite with family and friends begin to arrive in the United States.

Even so, it appeared that Monday’s reopening went relatively smoothly for airports across the country. Andrew C. Gobeil, a spokesman for Atlanta’s Hartsfield-Jackson airport, the nation’s busiest airport and the world’s busiest before the coronavirus pandemic, said operations were normal Monday.

In a statement, Homeland Security Secretary Alejandro N. Mayorkas hailed the reopening as “a critical step to resuming normal travel.”

The day was filled with elation in the United States and elsewhere, including an unlikely partnership of competitors.

Rival carriers British Airways and Virgin Atlantic timed departures from parallel runways at London’s Heathrow Airport to have the first flights filled with previously barred travelers land stateside. Both flights arrived at New York’s John F. Kennedy International Airport and passengers were greeted by balloons and cheers as they exited the plane.

“Today is a time for celebration, not rivalry,” Shai Weiss, chief executive of Virgin Atlantic, said in statement.

At Dulles International Airport outside the nation’s capital, travelers reunited with grandchildren in the terminal or hustled out to see girlfriends and fiances waiting anxiously in cars idling at the curb.

Army officer Ben Bennett, 40, holding a rose and a Stars and Stripes balloon, waited for a girlfriend he had met while serving in Germany during the pandemic.

“I’m super excited to have her here,” Bennett said, on his feet and watching the arrival door.

He said they were planning to go to Florida and visit Disney World. But the wait dragged on while his girlfriend went through customs in a line she estimated at 300 people.

Bennett took a seat, eyes flitting from his phone to the door. Then, she was there. They embraced.

The travel ban’s lifting — which brought similar reunion scenes to international airports across the country Monday — has been a boost for the travel industry, both in the United States and abroad. Carriers on both sides of the Atlantic pushed for more than a year to end restrictions and repeatedly expressed frustration that U.S. borders remained closed, even as other countries opened to vaccinated Americans this summer.

But all of that was forgotten as the industry counted down the days for the ban to lift.

“While we have seen many countries reopen their borders to American visitors over the summer, our international customers have not been able to fly with us or visit the U.S.," Ed Bastian, Delta’s chief executive, said in a statement. “All of that changes now.”

Under the new policy, most visitors from Europe, China, Brazil, India and South Africa can come to the United States as long as they show proof of vaccination and a negative coronavirus test. Children under 18 are not required to show proof of vaccination, but must be tested before they board flights.

Delta Air Lines said that in the six weeks after the Biden administration’s September announcement that it was lifting the travel restrictions, it saw a 450 percent increase in international bookings. American Airlines said demand from London’s Heathrow Airport and Brazil for this week were about 70 percent higher than the previous week.

United Airlines said bookings for transatlantic travel for November exceeded 2019 levels for the first time since the pandemic began.

The carrier’s first international flight of the day, from Dublin, touched down at Newark Liberty International Airport at 11:30 a.m., one of 33 scheduled United flights to arrive Monday in the United States. Of those, more than a half-dozen from countries previously covered by the ban were scheduled to land at Dulles.

Even as domestic travel began to recover this spring and some business travel resumed, many in the travel industry had said a full recovery wouldn’t be possible until the U.S. ended its ban on travelers from the 33 countries.

While carriers had been operating flights from several of the countries included in the ban, many seats that previously were empty suddenly were occupied Monday. Delta said many of its international flights were expected to be full, with high passenger volumes continuing for weeks.

The reopening, while welcome, may not be completely trouble-free, some caution.

“No one is expecting this to go without a hitch,” Harteveldt said. “We are only as good as the data and everyone is prepared for a stop-and-start environment, whether it’s their country or the U.S. If covid cases increase beyond a certain level or vaccine rates don’t reach a certain level, you know that borders may be closed again.”

But those worries were far from the minds of those at Dulles, who waited anxiously for glimpses of their loved ones.

Maureen Watkins, 64, tearfully scooped up one of her two granddaughters and marveled at how they had grown since she saw them early last year.

“Gosh you’re heavy,” said Watkins who had arrived from London. Once it was clear the restrictions would lift, Watkins said she knew she wanted to be on the first flight.

“Every bit of me is just shaking with emotion,” Watkins said, as her son, Elliott, daughter-in-law, Chloe, and their daughters Isla, 4, and Elsie, 2, gathered in the arrivals area.

Maureen Watkins said she plans to stay for two months. Chloe Watkins said the plan is to “eat, drink and be merry.”

Editor’s note: A photo cutline was changed to remove a traveler’s last name.