[elihu]

The article mentions that they have transponders that can be used but apparently in this case it was off or not working. They can also attach a radar reflectors when they want to be more visible to radar, and apparently the weapons configuration plays a role too:

> "Also, the jet's configuration and its avionics' operability are an issue. The F-35s wear radar reflectors when on transit flights, as well as on many training missions and some operational ones. The Marine jets often wear missile rails for AIM-9Xs, as well. But if the aircraft was in its full stealthy configuration and had avionics issues, tracking it may have been troublesome."