But the project is still at an early stage, with the defence ministry seeking 58.7 billion yen (US$560.9 million) in the 2021 budget for research to develop the aircraft.

Japan has yet to decide whether to develop a multirole combat aircraft or an air superiority fighter, but Jon Grevatt, an Asia-Pacific defence industry analyst at Jane’s, said it was more likely to go for a multirole warplane.

“It can perform as a fighter aircraft and ground attack aircraft, and it can also be used to perform other operations such as monitoring and surveillance,” he said.

The most important feature would be stealth, according to Grevatt.

“Stealth will be a very important priority for Japan … and the reason is because China – which Japan regards as its biggest rival – has advanced its capabilities very rapidly in the last decade to 15 years in terms of its sensors, radars and other surveillance capabilities,” he said.

“Any new fighter Japan is trying to develop must be able to evade the system. And of course, China’s priority would be to identify those aircraft.”

01:48

Powerful Dragon v Raptor: how China’s J-20 stealth fighters compare with America’s F-22s

Powerful Dragon v Raptor: how China’s J-20 stealth fighters compare with America’s F-22s

China’s rapid modernisation of its military has prompted Japan to press ahead with developing its own fighter jet, according to analysts.

Grevatt said that more warplanes operating in the region would create a bigger risk of miscalculation and misunderstanding between the militaries.

“In the next few years, China will be introducing its J-20, a real air superiority fighter,” he said. “It will provide hope and advantage for China, and a perceived risk for Japan – and also a motivator for Japan to develop its F-X.”

China’s J-20 stealth fighter shown in training dogfight on state television

Michael Raska, an assistant professor with the S. Rajaratnam School of International Studies at Nanyang Technological University in Singapore, also said pressure from China had pushed Japan to pursue its indigenous fighter jet programme.

“China’s military challenge poses significant dilemmas for US allies in East Asia. Japan must grapple with consequences of the Sino-US strategic rivalry – Tokyo must calculate its potential future role, the level of active participation, and defence resource allocation requirements supporting future US military strategy and operational conduct in the region,” Raska said.

02:31

The growth of Chinese military power over the past four decades

The growth of Chinese military power over the past four decades

His view was echoed by Bradley Bowman, senior director of the Centre on Military and Political Power at the Foundation for Defence of Democracies, a Washington-based think tank.

Bowman said it was clear that Japan believed it had to strengthen its domestic defence aerospace capacity in light of the growing threat from China.

“Beijing’s aggressive behaviour represented the primary catalyst for Japan’s eagerness to improve its defence capabilities … The US and Japan are engaged in a competition with China that revolves to a significant degree in defence technology innovation,” he said. “It is in the interests of both Washington and Tokyo for Japan to strengthen its defence research and development.”

He added that “the danger comes from the increasingly aggressive behaviour of Beijing”.

“There is no effective strategy for dealing with China in the coming decades that does not include an incredibly close defence partnership between the US and Japan.”

Japan prepares to freeze China out of its drone supply chain due to security concerns

But Raska noted that it remained to be seen whether Japan would be able to sustain the F-X programme in the long term.

“Tokyo has shown political willingness to do so, however there are many other technological, economic and strategic factors that must come together to succeed in the long term,” he said.