Thanks for the informative responses, especially cochise's explanations of the reasons why an IR ticket would be much less likely in Africa than in the States or Europe. I wasn't especially concerned at the time, as the fellow did have a backup plan (fly south, where the weather is always better) and he was clearly experienced with the area and its conditions. I too have enormous respect for the bush pilots I've seen in southern and eastern Africa: they exercise their profession in a very different world from one where navaids are reliable and omnipresent.