At the end of 2020 Japan decided to proceed with a two-decade old plan to design and build its own stealth fighter. This F-X/F-3 effort would only produce a hundred aircraft unless Japan obtains export customers. Until 2013 Japan refused to export weapons, since then such exports are allowed as long as they do not go to any nation at war or violate any arms embargoes. The FX project will cost $12 billion and the Japanese parliament provided $703 million in the 2021 defense budget to start work. Japan has been actively developing technologies for a new fighter for over a decade and for that reason the first FX prototype is expected to make its first flight in 2028 and enter service in the mid-2030s.
Japan has already developed and flown a stealth fighter prototype. This aircraft, the X-2, was made public in early 2016 after it made its first flight in April 2016. With that there was no point in trying to keep it hidden from public view anymore. Work on X-2 began in 2009 and at the time Japan realized it would take another decade to get the X-2 into service, assuming all the technical and fiscal obstacles could be overcome and the government agreed to provide the cash. At that time China and Russia were also trying to develop similar aircraft while the U.S. has already done so, several times, since the 1980s when the F-117 appeared.
The X-2 was actually a “demonstrator” aircraft for testing stealth concepts. The stealth tech that works would then be incorporated into what became known as the F-X. A new fighter was needed to replace the locally built F-2s by the end of the 2020s. At first it was planned to call the F-2 replacement the F-3 (or ATD-X). This version would have a lot less stealth and other advanced tech. The decision to go full stealth came about after Japan received its first F-35s and realized that the original X-2/F3 concept was too limited. Japanese F-35 pilots confirmed that the F-35 software was as essential as the stealth features and the reason why F-35 export customers have been increasing their orders once their pilots have experience with the F-35.
Japan was always aware that the FX option depended on how dangerous their neighborhood got. The Chinese and North Korean threats have increased over the last decade and FX is an effort to ensure the Japanese defenses keep up. The X-2 program was meant to prove Japan could develop and build a modern stealth fighter. The single X-2 prototype was not meant to become an actual combat aircraft, but rather a technology demonstrator that would make as many as 50 test flights and conclude the process in 2018. That is what happened even though the X-2 only flew 34 times. After 2018 it was a matter of obtaining foreign partners and money from the Japanese parliament to proceed to stage two, which is the F-X.
Meanwhile Japan decided to purchase 42 American F-35 fighters in 2011. These were needed to replace its 110 elderly F-4Js. The F-35A is a 31-ton, single engine fighter that is 15.7 meters (51.4 feet) long and with a 10.7-meter (35 foot) wingspan. The F-35A can carry 8.1 tons of weapons in addition to an internal 20mm four-barrel autocannon. Japan agreed to pay about $127 million for each F-35, which included training, maintenance equipment, and a supply of spare parts. The Japanese are assembling the F-35 in Japan as the AX-1 and some of the components will be made in Japan. Despite the AX-1 deal, Japan continued to explore the possibility of developing and building its own stealth fighter, especially since the Americans would not sell the F-22 to export customers. In 2010, wary of the continuing delays (and rising costs) of the F-35 program, Japan seriously considered buying another 50 locally made F-2s. This Japanese F-16 variant has a 25 percent larger wing area and better electronics than the original F-16. The 22-ton F-2 carries nearly nine tons of bombs. This plane is twice as expensive (at $110 million each) as the F-16, part of that is due to the better electronics (like an AESA radar), but mostly this is due to higher production costs in Japan. The F-2 has been in service since 2000 and 98 have been built so far. Once some Japanese F-2 pilots converted to the F-35 they reported that more F-2s were not the way to go.
Since the 1990s Japan has been concerned with the growing belligerence of China and North Korea, plus a simmering territorial dispute with Russia. More warplanes, and the modern ones at that, were needed just in case. Rapid Chinese development of its new stealth fighter, the J-20, also alarmed the Japanese. The delays in the F-35 program proved to be minor compared to the problems the Chinese and Russians encountered with their first stealth fighters. South Korea had the same idea, having also obtained nearly as many F-35s as Japan and also plans to develop their own stealth fighters.
All this is bad news for China, Russia and North Korea because if you do the math, it is clear that the modern warplanes available and planned for the local anti-China coalition (Japan, South Korea, Taiwan, Singapore, Australia and a growing number of South-East Asian nations) match what China has and, once you add American forces deployed in the Western Pacific, China is at a disadvantage. This coalition developed because China has been making territorial claims on many of the coalition members or otherwise threatening them. Absent that aggression there would be no coalition or arms race.