Sixth Form estimation question 2015 #2

Yesterday was a great day for viewing planes. I timed how long it took the plane to go from my little finger to my thumb - 22 seconds. My little finger is worth 1 degree. Compare the plane to my little finger to work out how many degrees the plane is worth. Then use a triangle method to work out how high up the plane is. Then work out how many miles the plane actually flies from my little finger to my thumb and calculate the speed of the plane. Comment on whether the speed is sensible.