These aircraft have some of the most sophisticated radars in the world and avoiding mid-airs comes down to dirty canopies?
BS, crew chiefs clean them before and after every flight, it's part of their pre-flight, thru-flight and post-flight checklists to ensure the canopy is inspected and cleaned if needed.
Unless the pilots are licking the windows during flight, I have a hard time understanding this "directive".
![shrug :shrug:](https://www.gopbriefingroom.com/Smileys/default/th_shrug.gif)