When Edith Yeung landed at Hong Kong airport around 6 p.m. on Monday, her plane’s crew announced that all connecting flights had been canceled, without saying why.

That was Yeung’s first inkling of the chaos that awaited thousands of passengers as Hong Kong’s international airport, the busiest in Asia, imposed an unprecedented shutdown after protesters swarmed into the terminal.

Yeung, a partner at the venture-capital firm Proof of Capital, waited in line with hundreds of others for an Airport Express train to the city center. The air-conditioning appeared not to be working, and at least one woman fainted in the heat and humidity of a Hong Kong summer, Yeung said. When all the passengers managed to squeeze on to the train, the doors wouldn’t close properly.

“I have never seen so many people on the Airport Express,” she said.

Others were left confused or scrambling for alternative arrangements as airlines canceled flights for the rest of the evening. The chaos quickly went global: Many scheduled flights to Hong Kong were canceled. A hastily written message in Takamatsu, Japan, for travelers with the budget airline HK Express read simply: “Departure time unknown.”

The shutdown was the latest move to disrupt transportation by pro-democracy protesters, who have rallied in the city’s streets for 10 straight weeks. The movement began as opposition to a bill—since shelved—that would enable extradition to China, but has morphed into a cry of anguish over Beijing’s encroachment on Hong Kong’s freedoms.

Increasing Violence

The sit-in follows weeks of airport and subway disruptions and increasingly violent clashes with police. During protests this past weekend, law-enforcement officers fired tear gas into a subway station and dressed up as protesters to tackled demonstrators to the ground. Hundreds have been arrested in recent weeks.

Dozens of passengers trying to reach the airport from Hong Kong Station, in Central District on Hong Kong Island, were standing around confused as displays showed flights canceled. One man traveling with his wife and daughter, who would give only his surname, Shen, said their plans to go to Australia looked to be in ruins.

“The protesters should compensate us,” he said, as he sat on the floor with his family.

A senior investment banker based in Hong Kong for a global firm, who declined to be further identified, said he was considering catching an alternative flight to Canada by driving across the border to Shenzhen, then flying via Beijing.

Another traveler to the departure terminal on the Airport Express from the city center described her train car as packed with chanting—but polite—protesters. The airport was as jam-packed as a nightclub, this person said, but many of the check-in staff had left. Confused passengers took to yelling at security staff.

Left on Tarmac

Others were stranded on the tarmac as protesters went through the airport handing out flyers, spray-painting graffiti and pasting up posters decrying aggressive police tactics against demonstrators. Some set up TV screens on cardboard boxes inside the terminal that played footage of police tactics from the weekend.

“We are telling the government that if they keep cracking down on the protests, Hong Kong people will do whatever we can to get our voice heard,” said a person surnamed Yip, an office worker who took part in the airport sit-in. “This is our last resort.”

Australia’s consulate-general in Hong Kong dispatched officers to help escort Australian tourists out. With traffic at a standstill outside the airport, many people abandoned taxis and buses and walked.

As rumors spread that riot police were on the way, large numbers of protesters left in the late afternoon, walking alongside highways instead of waiting for packed trains. Hundreds more stayed in the terminal into the evening.

“Liberate Hong Kong,” they chanted. “Revolution of our time.”

One sign held up by a protester read: “It’s a few hours of your time, but it’s our lives at stake.”