Hong Kong's Airport Authority said on Tuesday it was working with its partners to restore normal operations as soon as possible but noted that more protests are planned.
The Airport Authority halted flights to and from the airport on Monday, citing disruption from anti-government demonstrators who had peacefully occupied the arrivals hall since Friday.
Increasingly violent protests have plunged the Asian finance hub into its most serious political crisis in decades, posing a challenge to the central government in Beijing.
"The AA has noticed that there are calls online for public assembly in the airport this afternoon," the authority said in a statement. "The AA will work closely with its business partners with a view to gradually resuming normal airport operations as soon as possible."
Meanwhile, Cathay Pacific issued a statement on Tuesday encouraging customers "to postpone non-essential travel from Hong Kong on Tuesday 13 August and Wednesday 14 August and should not proceed to the airport unless they have a confirmed booking."
Hong Kong's airport reopened on Tuesday but its administrator warned that flight movements would still be affected, after China said widespread anti-government protests that halted flights a day earlier showed "sprouts of terrorism."
Despite the airport reopening, Hong Kong flag carrier Cathay Pacific said it had canceled over 200 flights to and out of the airport on Tuesday, according to its website.
The airport, one of the world's busiest, blamed demonstrators for halting flights on Monday, but the exact trigger for the closure was not clear as protesters occupying the arrivals hall for the past five days have been peaceful.
— CNBC contributed to this report.