It’s not just about stealth. Sensor fusion is also a key aspect of the F-35. With no second crew member, and the traditional head-up display replaced by a sophisticated helmet-mounted display, this combat jet is very different from all that have gone before. It has over nine million lines of code. Five air system software releases precede the definitive one.

The new generation fighter has been a long time coming – 15 years since Lockheed Martin won the Joint Strike Fighter (JSF) evaluation, and three years behind the original schedule. Along the way, many have doubted whether it was wise to try and meet three distinct airpower requirements with one basic airframe. The demanding short take-off and vertical landing (STOVL) requirement for the F-35B part-caused led to a major weight crisis that affected the land-based F-35A and carrier-based F-35C versions too.

 Our summary of the latest report on the F-35 by the U.S. Director, Operational Test and Evaluation (DOT&E) is a reality-check on progress. Affordability is a big issue, as we discussed here for the airframe, and here for the engine. Concurrency is a third major concern: early production aircraft must be retrofitted with structural fixes.

Inevitably, though, an aircraft designed in three very different versions will be complicated and controversial. The first to go operational was the F-35B of the U.S. Marine Corps last summer. The U.S. Air Force F-35A is due to follow later this year, and the U.S. Navy F-35C in 2019.

The most problematic part of the program appears to have been the Autonomic Logistics Information System (ALIS), as our recent report makes clear. The helmet-mounted display (HMD) was threatened with replacement, but has now been confirmed. An engine rubbing problem that prevented the F-35’s international debut in mid-2014 was fixed nine months later.

Eight nations signed up as partners on the F-35 program, but some have expressed doubts, and considered alternatives. Israel, Japan and Korea are also customers. Most recently, Denmark reconfirmed its choice but (as with the Dutch) for lower numbers. Of course, there are industrial benefits, such as a production line in Italy. A few months ago, we ran this story about how Australia is preparing for its jets.