China's leading aircraft manufacturer is on the verge of exporting its fifth-generation fighter jet, according to industry sources.

Aviation Industry Corp of China disclosed the technical specifications of the J-31 Gyrfalcon at an aviation expo even though the plane was still being tested, the sources said.

During the four-day Aviation Expo China 2015, a biennial event held in Beijing in mid-September, AVIC also displayed a large-scale model of the J-31.

Expo visitors were surprised that the State-owned defense contractor was willing to declassify the J-31's specifications, as it had never previously released such information on military air-craft until they entered mass-production and were ready for export.

Analysts said the decision indicates that the corporation wants potential foreign buyers to learn about the plane's capabilities as soon as possible so that it can secure contracts when the jet becomes operational.

A source close to AVIC who declined to be named said publication of the aircraft's specifications was aimed at impressing potential buyers.

"The earlier the buyers know about the J-31's capabilities, the higher chance AVIC has of taking up a good share of the fifth-generation aircraft market," he told China Daily.

"Once the company receives buyers' payments, it can use these to sustain the production line and continue to upgrade the aircraft to win more customers."

AVIC executives have never concealed their intentions for the J-31 project.

Li Yuhai, deputy general manager of AVIC, told reporters in November, "Since the start of the J-31's development, we have planned to use the plane to end some foreign nations' dominance of the fifth-generation fighter jet. One of its variants will be specifically designed for export."

Li was speaking on the sidelines of the 10th China International Aviation and Aerospace Exhibition held in Zhuhai, Guangdong province.

Chen Hu, a military expert with the People's Liberation Army, said exporting the J-31 would be a milestone for China's aviation industry because the plane would give AVIC a significant boost in competition with Western defense giants.

Xu Bangnian, a professor at the PLA Air Force Command Institute, said he expected international demand for the plane as it appeared to be the only choice for developing countries wanting an affordable fifth-generation stealth aircraft.

The only fifth-generation fighter jet available on the market is the United States' Lockheed Martin F-35 Lightning II, but the US will only sell it to its allies.

The J-31's maiden flight in October 2012 caused a surprise globally, as few people expected China to develop another fifth-generation fighter jet following the J-20 stealth aircraft, which made its first flight in January 2011. During the past three years, the J-31 has undergone several test flights and some changes have been made to its design.

The AVIC specifications show that it has a maximum takeoff weight of 25 metric tons and is designed to be in service for up to 30 years.

zhaolei@chinadaily.com.cn