Pro-democracy protesters had taken over the Hong Kong airport over the weekend. Flights were cancelled in light of protestors in the airport. The government was trying to send reassuring messages to travellers so that they were not discouraged from visiting the city. But the airport had to be shut down as protestors flooded the airport.
Authorities are now trying to reopen the airport.
China's government signalled its rising anger at the protesters, denouncing some of the violent demonstrations during the weeks of unrest as "terrorism".
The United States urged "all sides" to refrain from violence and Canada called on Beijing to show restraint.
Authorities said they sought to reopen the airport at around dawn on Tuesday, but hundreds of protesters had remained in the arrivals hall well into the night. Protests that began 10 weeks ago to oppose an extradition bill has now turned into a pro-democracy movement. This is one of the biggest challenge to the Chinese rule since the British colony was handed over to China. The city has been enjoying the one country two systems module, with the financial hub enjoying more autonomy. The city will automatically lose autonomy in 2045, and citizens fear they will immediately be pulled into communist rule under China.
The airport listed some long-haul flights of other airlines as having departed overnight while others had landed.
Other flights, within Asia and beyond, are scheduled throughout Tuesday morning but many were still shown as cancelled.
Although other rallies had been held there over the previous three days, causing more than 250 flights to be cancelled. The airport normally handles around 2,00,000 passengers a day.
Over the weekend police fired tear gas into subway stations and crowded shopping streets in confrontations with protesters at nearly a dozen locations across the city.
Protesters responded by hurling bricks and spraying riot police with fire extinguishers and water hoses.
They were also angered at the police who have resorted to wearing black t-shirts just like the demonstrators do, in order to infiltrate the rallies and make surprise arrests.
"It is becoming more and more dangerous, but if we don't still come out at this point, our future will become more frightening, and we will lose our freedoms," said one 22-year-old protester who gave her family name as Chan.
The city's transport chief Frank Chan said Monday that Hong Kong would pay a "heavy price" for the airport's closure.
A senior official in the administration of US President Donald Trump on Monday urged "all sides" to avoid violence in Hong Kong.
"Societies are best served when diverse political views are respected and can be freely and peacefully expressed," the official said on condition of anonymity.
Canadian Prime Minister Justin Trudeau called on China "to be very careful and very respectful in how it deals with people who have legitimate concerns in Hong Kong".