Japan's ATD-X First Flight.

Japan's Advanced Technology Demonstrator-X (ATD-X) fighter test platform will not fly until at least late 2015 due to issues with the software that controls automatic engine restarts, according to officials at the country's Ministry of Defence (MoD).

Japan's ATD-X First Flight.

The first test flight was scheduled to take placebefore the end of the current financial year in March, but the problems affecting the engine control unit (ECU) will require several months to resolve.

The ECU is a critical safety and power management system that automatically reactivates an engine if it shuts down in flight.

MoD officials said that the current issue is a software fault. Rather than using existing off-the-shelf systems, much of the technology installed in the ATD-X was developed especially for the project and so solutions need to be developed from scratch, contributing to the current delay.

MoD officials expect work on the ECU to take several months, but due to the experimental nature of the work required the true scale of the delay is unknown.

ATD-X's main contractor, Mitsubishi Heavy Industries (MHI), is building a single test aircraft at its Komaki Minami plant in Aichi Prefecture that uses a smaller planform than a potential production model.

The MoD's Technical Research and Development Institute (TRDI) has been working on ATD-X since 2009. The project grew out of Tokyo's concern that it lacked the technical know-how to build a 'fifth-generation' fighter, concerns that grew more acute following the 2006 US Congressional ban on exports of the F-22 Raptor.

Japan will decide in 2018 whether to put the technologies developed by TRDI to work in a domestically built stealthy air-superiority fighter to replace its F-2 fleet, or whether it will seek to develop a new fighter in partnership with other nations.