It's not just the black aircraft!
. . . and it's been going on for years. I worked for the Red-White-Blue at Heathrow some time ago and there was a panel on the 747 sim overhead that was blanked normally.
Periodically we had a visit from a different instructor and the sim engineers were rarely called for snags during these (usually night-shift) sessions. Once or twice I noticed after these sessions that the blanking panel was not fastened as it had been before, and behind it was a plug that was not connected to anything!
If that doesn't get you thinking then nothing will!!!!! Listen to Shattered - he's onto something.