The NATO phonetic alphabet is the most widely used radiotelephone spelling alphabet.
Its use ensures clarity in transmission of critical information, commonly used in military and aviation communications.
Do you know all the letters? 
Discussion
Had to learn when working for a global hosting provider at their Network Centre as a network analyst.
When calling customers or other DCs you'd sometimes get hit by bad signal and/or lots of static, so using the NATO phonetic alphabet just made everything go smoother.
I once blanked on U.... In a panic, went with Unicorn. Biggest laugh I gave my team. Good times hacking on networks.