I have long believed that aircraft could see me even in cloud and have posted on it here on occasion. Invariably I’m told that they are listening to the sound and or getting lucky.
I was just in European Province. I spawned into my Me 262 over heavy overcast. I could clearly see two other planes even though all of us were in separate, heavy clouds.
At first, I could see them as dark spots up against the white clouds. As I entered a darker portion, I could see a sort of white halo around them. My plane is without radar and I was about 11 km away, a distance at which I cannot see aircraft normally, and they were perfectly visible. And no, no one is hearing anyone at that distance.
And they could obviously see me too, as two MiG-15s and a Beagle all immediately converged on my location in the middle of a pitch black cloud.