Really strange.
Heathrow isn’t very welcoming in terms of weather, but I see multiple British Airways aircraft flying in and out right after starting the flight:
Actually sometimes more crowded than I’d like to 
Funnily the forum software compresses the images so that the clouds look all colorful (purplish) but ingame they look perfectly gray.
And there are quite many in the vincinity:
Comparing with Flightradar24, it seems to match the real world quite well.
Try turning off Data in the general options and turn it on again, maybe something is stuck. But in general it should work (North Europe server here).
Here are my settings for comparison:
