The major requirement for ground instruction is professional aircrew experience either civil or military. As most of the exam material is military in origin military navigators are a favourite together with flight engineers and pilots with one leg.
As there is a shortage of people with the desired experience, a technical degree and teaching experience is a common starting point.
At the end of the day you need to be familiar with the material you are going to teach.
[This message has been edited by Noggin (edited 30 January 2001).]