... as to _how_ bright it can be - I was once in an area with dark skies, setting up my telescope just before sunset. After dark, I was taking in the beauty of the Cigar Galaxy and then looked up and behind from the scope. My eyes were assaulted by a bright light on the top of the hill behind, and I was cursing the idiot who had turned that light on, when I realized that it was Jupiter, freshly risen above the hill. Jupiter is not as bright as Venus.

On that night, Venus, had it been visible, would've been blindingly brilliant. Flying 10 Km above the ground, with no light pollution, I'm not surprised that the Pilot mistook Venus for an aircraft headlight.

Edit: clarity