If it's a clear day and the bottom of the airplane is painted blue, it could blend in with the sky. For that matter, didn't Wonder Woman have a transparent airplane?
Aha, better yet, it was invisible! https://dc.fandom.com/wiki/Wonder_Woman%27s_Invisible_Plane
Yes, because if there's one thing computer vision solutions have historically had trouble with, it's being fooled by paint. The ludditism in this thread is shockingly strong.
CV systems absolutely do struggle with this...
Yes, and that's considered a bug to fix, and can be. CV systems are widely applied to find camouflaged and obscured objects! Literally every automated wildlife camera is proof that this is a silly point.
Call it whatever you want, lack of contrast is a physical constraint on your system and can be trivially leveraged. There's been an arms race between optical camouflage and detectors for the entire history of eyes.
It's not necessarily a game ender, but it's not something you can just wave away either.