Cathay Pacific flight CX 841 from New York to Hong Kong was diverted to Beijing as a passenger required urgent medical assistance, the carrier said.
There were 239 passengers on the flight, which landed in Beijing at 11:20 a.m. local time, Cathay Pacific said.
The diversion comes amid increased nervousness about terrorism globally after deadly attacks in Paris 11 days ago. Belgium's capital Brussels was on lockdown for three days, with schools closed and metros halted, as police conducted raids in and around the city, searching for suspects in the Paris attacks.
Concerns have also been raised after a Russian Metrojet plane crashed in Egypt last month, with a bomb suspected to be the cause. Islamic State terrorists have claimed responsibility for both attacks.