Light streak in the sky, April 5th 2020

I stumbled upon a weird streak of light on one of my older images by pure accident, something I only discovered now and did not see when I took the images at the time. Other photos taken 10 seconds before and 12 seconds later don't show anything unusual at all.

The photo was taken while flying track 066' over the Atlantic Ocean on April 5th 2020 at 20:37:27 UTC. Location was just south of Nova Scotia, 45°27’N 60°47'W at 41,000 ft.
Camera used was the Nikon D850 + Nikon 14-24mm f/2.8 ED for this shot with the following settings: 22mm, 1/4000s, f/6.3, ISO160 and autofocus. Images are 100% unedited, extracted from RAW image.

I'm breaking my head over what could have caused this flash of light. Judging from the shutter-time of 1/4000s, something moved at incredible speed with pretty consistent and extreme brightness, possibly reflecting sunlight. Looking forward to serious analysis of the speed/size/nature of this light, taking into account shutter-time and relative altitudes/distances.

Zooming in on the light streak it shows various colours: this could be an artefact of the glass lens elements.

Open to all serious suggestions to what this could have been.
 

Possible explanations:

• Meteor / shooting star:
  Meteors generally tend to move much slower and not as bright as this one. Never seen one during daylight. Even if it would be a daylight meteor, it would probably have been a major explosion like the Chelyabinsk meteor. A meteor would have left a bright contrail in its wake as well and shown up on other photos. Unlikely.
   
• Space debris / discarded rocket booster burning up:
  I've seen a couple those events and they tend to move rather slow and break apart spectacularly in a group of lights during their fiery descent. They looked nothing like this.
   
• Satellite/ISS:
  Would match the size, but neither the speed and brightness. Unlikely to see them during daylight.