Skin.

This is coolbert:

"Much of what makes up and lies beneath the F-22 Raptor's silver skin remains a tightly guarded secret. The aircraft's outer mold-line is a mosaic of radar-absorbent coatings and radar transparent and radar defeating composite structures that combine to allow the Raptor to remain aerodynamically efficient while also largely invisible to fire control radars. All this takes a lot of work to maintain and many of these applications start degrading shortly after they are applied, with friction from high-speed flight, crushing G forces, and the elements accelerating that process. As such, one of the costliest aspects of operating F-22s—and flying this aircraft is extremely expensive with an average flight hour cost of about $60k—is keeping its stealthy skin up to par. This also is a major contributor to its fairly abysmal mission capable rate of around 50 percent."

First from "The Drive":

1. "These Images Of An F-22 Raptor's Crumbling Radar Absorbent Skin Are Fascinating"

"The photos are a reminder of just how much work goes into keeping the F-22's skin ready for combat and the amazing science behind its stealthy design."

Cost per flight hour F-22 immense. Maintenance a major factor as to cost and a big problem. with aircraft down-time. A dedicated staff required to maintain just the stealth skin.

Yet more from "The Aviationist".

2. "There’s Now A Second ‘Chrome’ F-22 Raptor Flying With Mirror-Like Coating At Nellis AFB"

"A second 'Chrome' F-22 has been spotted at Nellis Air Force Base operating alongside other aircraft taking part in Red Flag exercise."

"As we [Aviationist] have reported in detail last year, there’s a sort of mysterious F-22 Raptor flying over Nevada since November. First caught on camera on Nov. 19, 2021, the unmarked stealth aircraft sports a peculiar 'mirror-like' coating, never seen before on a Raptor."

High-tech "skin" stealth coating of the F-22 being replaced with some sort of chromed surface?

Also additionally the radar abosorbing material [RAM] as applied to the various stealth warplanes:

3. "The Science of Stealth"

"The most classified technology in a stealthy airplane is its skin"

Everything you always wanted to know about stealth coating but just never know what to ask.

AND IN ALL CASES EXPENSIVE!

coolbert.