Activists dressed in black sat in the arrivals hall waving banners to raise awareness among international visitors.
Protests have gripped Hong Kong for weeks, beginning with anger at an extradition bill and morphing into demands for greater freedoms.
The former British colony is part of China but enjoys more autonomy.
It has a free press and judicial independence under the "one country, two systems" approach - freedoms activists fear are being increasingly eroded.
They have called for an independent inquiry into alleged police brutality during the protests, the complete withdrawal of the controversial extradition bill, and the resignation of Hong Kong's leader Carrie Lam.
At a press conference on Friday, Ms Lam spoke of the economic impact of the protests after meeting with business leaders. She called on people to stop taking part in protests and for an end to the violence.
"We should put different opinions aside so that Hong Kong society won't be hurt further," she said.
Beijing earlier this week warned demonstrators not to "play with fire" or to "underestimate the firm resolve [of] the central government".
Demonstrators plan to stay at the airport throughout the weekend.
They are waving banners written in different languages denouncing Carrie Lam and the police, and handing out leaflets with artwork explaining the recent protests.
Authorities are so far tolerating the peaceful rally, which have not overly disrupted passengers. There are as yet no police at the scene.