I think you are thinking of these recent photos of an F-22: https://www.thedrive.com/the-war-zone/29218/these-images-of-an-f-22-raptors-crumbling-radar-absorben

I think you are thinking of these recent photos of an F-22: https://www.thedrive.com/the-war-zone/29218/these-images-of-an-f-22-raptors-crumbling-radar-absorbent-skin-are-fascinating https://www.thedrive.com/the-war-zone/29218/these-images-of-... However you're no doubt correct that radar absorbant materials is high maintenance on any aircraft.