What are the screen like parts on stealth fighters?

[Ronny]

They appear on F-35 and J-20, do anyone have any ideas what are these screen thingy?

 

[overscan (PaulMM)]

Intakes, exhausts. or even covers for sensors.

 

[Hanse]

Basically, it's a way of having a hole in the skin without it looking like a hole on radar.