Flights at Hong Kong airport have resumed but authorities warned journeys would still be affected.
Anti-government protests forced the closure of the airport on Monday, resulting in the cancellation of hundreds of flights.
Flights from Boston, Bahrain and Sydney arrived at the airport on Tuesday but around 80 Cathay Pacific flights were cancelled to Asia.
The FCO has advised passengers to check their flight status with their airline and on the Hong Kong International Airport website.
Thousands gathered at the airport on Monday as part of demonstrations which started in June in opposition to a proposed extradition bill which would allow suspected criminals to be sent to mainland China for trial.
Leaders of Canada and Australia have called for a de-escalation of tensions in the city.
Hong Kong leader Carrie Lam warned anti-government protesters not to push the city into an “abyss”, during a press conference on Tuesday.
She said Hong Kong had “reached a dangerous situation” and that violence during protests would push it “down a path of no return”.