Read more in Daily Special: Bomb hoax grounds 5 flights

Three Chinese air carriers on Wednesday were targeted by false bomb threats involving five airplanes.

China Eastern Airlines received a call from an anonymous tipster at around 8 am saying that MU2325, a flight from Lanzhou to Xi'an, was in danger, a spokesperson told the Global Times.

The other two air carriers also received similar calls around the same time, sources said, quoting the tipster as saying that there were bombs on board.

Juneyao Airlines received a threatening call and arranged for a flight departing from Shanghai to return for checks. No danger was posed to the plane and the flight went ahead on another plane after all passengers and luggage went through safety screening.

Shenzhen Airlines received multiple threats, with flight ZH9866 departing from Nanjing returning after taking off. Flight ZH9243 from Xi'an was forced to land in Guilin, while flight ZH9889 from Beijing was delayed.

The Civil Aviation Administration of China said the police are tracking down the suspect who made the threatening phone calls.

Yang Jingjie, a passenger on ZH9866, which took off at 7:40 am from Nanjing to Shenzhen, told the Global Times that the plane returned an hour later.

"I saw many police cars, firefighters and even ambulances when we returned," Yang said. Passengers went through another round of security checks, he said, adding that the plane took off again around noon and landed safely two hours later.

A spokesperson for China Eastern told the Global Times that the effect of the threatening calls was "minor" and all flights have resumed, refusing to disclose how many flights had been affected.

Ruan Qilin, a criminal law professor at the China University of Political Science and Law, told the Global Times that the suspect would be charged with making up and spreading fabricated threatening information, and could be sentenced to up to 15 years.

"The calls caused tremendous economic losses and disturbed the social order," Ruan said. "This could be considered as a severe violation."

A suspect surnamed Xiong was sentenced to four years for calling Shenzhen Airlines in August last year, saying there was a bomb on one of its flights, causing the plane to be grounded.