More radio interference is occurring during flights as planes and routes increase and more airports are built, a senior civil aviation management official said.

Small radio stations that illegally boost their signals are adding to the interference, an industry expert said.

Western regions in China report fewer radio-interference cases compared with other parts of the country, a division chief with the Civil Aviation Administration of China, who did not want to be identified, told China Daily on Friday.

"Radio interference can be dangerous because it could mean a temporary or longer connection outage between a plane and traffic management on the ground," said the official.

Zhao Yifei, a professor studying air traffic management at Civil Aviation University of China, said radio interference mainly comes from radio station signals.

Civil aviation radio has its fixed frequencies through which planes maintain contact with traffic management on the ground. But signal frequencies of the small radio stations are close to those used by civil aviation, and some radio stations, mostly small ones, interfere with aviation radio when they boost their signals without authorization, he said.

A recent case occurred on July 12, when the captain of a plane flying from the southwestern city of Chengdu in Sichuan province to Wuhan, capital of Central China's Hubei province, heard a pop song from a radio station at about 8 pm while talking to air-traffic management staff on the ground, the Wuhan Evening News reported.

On May 23, more than 10 flights were delayed in Guangzhou Baiyun airport in Guangzhou, capital of South China's Guangdong province, because of severe radio interference in Hubei airspace, according to the newspaper.

Hubei airspace has become the region most vulnerable to radio interference in central and southern China, said a publicity official from the province's air traffic management bureau.

"From January to June, 197 flights reported interference from radio signals while flying through Hubei airspace," said the official, who only gave his surname of Liu.

One pilot with two years of flying experience said he once experienced radio interference during a flight.

"I was en route from Beijing to a northeastern city last year, but when I was talking to the traffic management on the ground, I heard some broken conversations in my earphone," said the 27-year-old, who declined to give his name because he is not authorized to speak to the media.

"I'm not sure it was a radio program or a conversation between the captain of another plane and traffic management staff. The radio system returned to normal about half a minute later."

The pilot said each plane usually has two radio systems, and if one does not work, the pilot uses the other.

"If both of them had interference, we would have to find ways to get in touch with other planes nearby so as to help send our message to traffic management on the ground," the pilot said.

The official with the Civil Aviation Administration of China said it has two monitoring planes to detect radio interference.

"We will carry out regular inspections, once every two years in general, on nationwide airspace over airports so as to detect radio interference and eliminate it," she said.

Zhao Yifei, the professor, suggested more efficient regulation of radio stations in order to better ensure flight safety.

Contact the writers at chenxin1@chinadaily.com.cn and zhoulihua@chinadaily.com.cn.