The China Southern flight landed in Gansu province's Lanzhou city Monday night several hours after departing Urumqi, the capital of the restive Xinjiang region. The flight originated in Istanbul and was heading to Beijing after the stop-off in Urumqi.
The official Xinhua News Agency said the flight resumed after a four-hour security check.
The latest report said the detained man, surnamed Wang, confessed to fabricating the threat, but it did not say whether he called in the warning or was on the plane. Xinhua said police were investigating the motive.
The incident follows a hoax in August that grounded a Shenzhen Airlines flight. Xinhua reported that police said the suspect in that case confessed to making up the threat to stop a creditor on board the plane from collecting his debt.
Xinjiang is home to the traditionally Muslim Uighur ethnic group. Long-simmering resentment among Uighurs over rule by China's Han majority has sporadically erupted into violence.