This plane stood out today because of the length of its vapour trail. I'd noticed one the other day that stayed constant at about 3 plane lengths but this trail covered half the sky. I estimated that the plane itself blocked out perhaps 2 degrees of my vision when overhead. I'll think about how I can measure this more accurately. Two degrees is about 0.02 radians, where a whole circle, 360 degrees, comes out at 2pi radians. I know that I can calculate the height of the plane using the arc length formula, where angle in radians = length of plane/height above me. I estimate the length at 70m. This means that the plane was flying at 70/0.02 = 3500m or just over 2 miles up.
