[electromagnetic]

I think it's that so much of our orientation is dependent on peripheral vision. I know Canadas worst pile up was caused by a heavy fog. 87 vehicles piled up, they believe in a very short time from the fog rolling in. The main factor was speed, basically people were over driving their view distance. Visibility was estimated to be something like 50 meters, but driving at 110kph gives you a stopping distance of around 150 meters. What worsened the incident was that light fog generally reduces drivers speed, but heavy fog is known to increase speed as the lack of peripheral markers means people can't gauge their speed and too few drivers check their speedometer.

I'm sure a pilot in dense cloud has the potential to make a whole host of mistakes. First I'm sure without instrumentation a pilot would quickly lose gauge on how level they're flying, or second guess how level they're flying and try to adjust. If you get caught in a cloud with a very low ceiling, there's probably not much time between exiting the cloud and that "Oh shit, that stuffs the ground". Or a slight climb and not enough thrust could easily compromise your speed and put you into a stall.

I'm quite sure 3-dimensions of travel is a real bitch when you're blind and can't stop.