Coming back from CDG to Seattle a couple of days ago.
Aircraft was an Air France A330 (Nice ride and half decent food.)
Altitude 40,000 ft, OAT -62C, GS 898Km/Hr (Can't get airspeed or Mach no from the SLF TV screens.) Somewhere over Edmonton AL.
Looked out of the window and saw what looked like the edge of a piece of glass jumping around on the wing. Displacement of the sight of the black front edge of the aileron and extending down to front edge of the middle of the spoilers. Movement of my eyeline in the window showed it was vertical, slightly curved (bowed aft)
Surprisingly I managed to get a picture on my point and shoot and I have cropped the middle bit. You can't see the less clear lower part where it is lost in the white of the wing.
The effect stayed around for a few minutes intermittently, disappeared for a while and then reappeared for a further few minutes.
It is not a shadow,
It is not a mark on the window
It is not a reflection
From moving the sightline it clearly appeared like the vertical edge of a piece of glass standing on the wing.
Was it a shock wave distorting the view?
I am curious and wonder if someone knowledgeable can enlighten. I really don't need the comments from ignoramouses telling me "Not to worry, the wing tip isn't falling off."