The first is a report from the GAO revealing the least well kept secret in defense procurement, that the JSF is over budget and behind schedule, to the tune of about $2 billion, the GAO also believes that the F-35 will need about 1000 additional flight test hours than the F-35 Joint Programme Office (JPO) does, and notes that the time to assemble the first production airframes was 40% greater than predicted.

Additionally, as I have noted before, it appears that there are some very concerning issues regarding thermal management for the aircraft, and it looks like the fuel-air heat exchanger, which not only cools the avionics, but the electro-hydrostatic flight controls is not sufficient in hot weather conditions, like the Middle East.

Additionally, the author of the linked article, Bill Sweetman, notices another potential heat issue, this one having to do with IR signature, that the location of the exhaust for the integrated APU/EPU exhaust has been relocated in the production models.

In the pre-production models, it was located on the top of the aircraft in front of the left vertical stabilizer (you can see where the heat cooked off the paint in the top picture), but in the production models, it has been relocated to the bottom of the fuselage.

The exhaust does not look particularly stealthy from a radar perspective to my untrained eye, and I would have to imagine that it would be a big infra-red “kick-me” sign for Marine STOVL JSFs which would be minutes from the battlefield with APUs running on unimproved strips when the aircraft is used to provide close air support.