Just a few weeks ago we flew from London to Venice. It was a lovely sunny day with some cloud cover as we crossed the English Channel so I pulled out my trusty camera and took a few shots. We crossed France and had a BA snack breakfast and as we approached the Alps the cloud cover started to solidify into a quite low level continuous layer at approx. 1500 to 2000m. I pulled the camera out again thinking I might be able to get some nice mountain shots. However before we got to the mountains I noticed the following circular pattern in the clouds.
I have a suspicion about what has caused this but would like others to comment. As you can see in the not very clear shot of the trip monitor displayed in the aircraft cabin (I had the presence of mind to photograph it) we are not that far from Geneva at 10,000m elevation.
The times shown are Australian EST because that is what the camera was set to (the date was 2nd Sept 2015 Aus. EST) so subtract 10 hours for GMT.
What do you think it might be?