Air China says it received threats against two of its Beijing-bound flights shortly before they were scheduled to take off, prompting it to perform security checks on both planes. It says nothing abnormal was found.

The airline said on its official microblogging site that it received the threats Tuesday afternoon before the flights from Lhasa and Nanchang were to depart. It did not describe the threats.

The threats came a day after a China Southern Airlines flight made an emergency landing after receiving a false terror threat. Chinese police detained a man suspected of making the threat. The plane had departed from Urumqi, the capital of the restive Xinjiang region.

The incidents follow a hoax in August that grounded a Shenzhen Airlines flight.