For all of the F-35 models you can find pictures with and without a blister on the upper wing surface. I'm guessing that it is sensors for the missile warning system that were retrofitted later on, but I couldn't find any information supporting that. F-35B without blisters F-35B with blisters F-35A without blisters F-35A with blisters F-35C without blisters F-35C with blisters


Those are Luneberg Reflectors.

They enhance the radar cross section of the aircraft.

For two reasons; to be more safe around civilian traffic due to being easier spotted by traffic control radars, and where they do not want adversaries to train their radar systems on it to gain knowledge of its strengths and weaknesses.

Not sure if those on the picture is retractable, or has to be fitted/removed by mechanics.

There are many sources for this, here is one: https://www.businessinsider.com/f-35-luneberg-radar-cross-section-russia-estonia-2017-5?r=US&IR=T

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    $\begingroup$ Do you maybe have a source for that? The positioning seems counterintuitive to me since the F-22 places its Luneberg Reflector on the belly of the aircraft where it is well in the line of sight for ground based radar, while I guess the ones on the F-35 would be quit well hidden from ground based radar. $\endgroup$ – hph304j Jun 22 '19 at 16:15
  • $\begingroup$ added a random source $\endgroup$ – Invariant Jun 22 '19 at 16:17
  • $\begingroup$ @hph304j There is one on the underside as well $\endgroup$ – DeepSpace Jun 22 '19 at 17:08
  • $\begingroup$ Nice find and +1, but how does it make it more safe around civilian planes? Civilian planes typically use TCAS which won't be affected by those reflectors. $\endgroup$ – ymb1 Jun 22 '19 at 19:32
  • $\begingroup$ edited to answer that better $\endgroup$ – Invariant Jun 23 '19 at 1:47

Yeah, they’re radar reflectors used during peacetime operations. They are removed prior to combat flight ops.

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