The Japanese government has selected the American Lockheed Martin F-35 stealth fighter jet to upgrade its aging Air Force. The plane will be used to upgrade the Japanese fleet, which includes some F-4s of Vietnam War vintage.

The decision is a major victory for the American aerospace industry whose leading competitor was the European built Typhoon. Japan is expected to buy between 40 to 50 jets, with deliveries beginning in 2016.

Japan needs the US to counterbalance China and Russia and the strong defense ties between Washington and Tokyo exerted an impact in favor of the F-35.

In addition to being used by the U.S. Air Force Marines and Navy in various configurations, the plane has support from Britain, Australia, Canada, Israel and other European nations. If more F-35s can be sold, research and development costs are amortized quickly, allowing a lower per unit price for the plane and making it more economically attractive.

The F-35 was the most costly amongst the competing planes, but the Japanese calculus is influenced by the persistence of boundary disputes with China and Russia - and the increasing intrusions of the Chinese and Russians into Japanese airspace.

When the Chinese unveiled their own J-20 stealth fighter, this convinced Tokyo that it had to go all the way to a 5th generation airplane rather than taking the less costly intermediate step of buying more F-15 jets.

Another inducement for the Japanese is the prospect that Japanese firms will eventually be subcontractors in the production, including assembly of the plane. In order to facilitate increased Japanese participation in joint development projects, the Japanese may be relaxing the weapons export ban, a throwback to Japan's pacifist traditions. If the ban is relaxed, planes partially assembled in Japan could also be used for the export market.

The United States would currently welcome greater Japanese participation in research and development so to reduce development costs.