Aircraft Adjacent tto Attacked Hex?

[garbare83686]

If aircraft are placed on top of their attacked hex a per 15.11 4th,  how and why should they get the +2 column shift for attacking adjacent units as stated in 15.13 4th?

Look at it a a direct fire unit with the adjacent part being the altitude of the plan related to the troops. Don't forget to roll for a successful target by the airplanes. I have been sorely disappointed when my air support can't follow simple directions and bomb the wrong place.