You assume that certification needs to fall within a particular discipline. And you have probably also assumed that "college" is at least approximately equal to "university", which is not the case in Ontario, Canada. What was required was a Teacher of Adults certificate and demonstrated competence. Short of posting my entire resume, I'll just say that there are areas of military avionics that require a little more than the mere ability to use an oscilloscope, and that I had had teaching experience in the interim period.