The thing is, these guys don't have FAA or EASA licences, nor the means to convert their ICAO licenses. It is not super difficult to get an FAA license, or that expensive, but it is hard to get a work permit/green card. On the other hand, it is really expensive to get a EASA license, and then work permits is also an issue. For most airlines you also need a degree, none of these guys have a degree. It is not impossible, but it is super challenging to get a job in the airlines if you are from this neck of the woods. I think there is a bout 20-25 expats left (if that many) there is about 100 Botswana pilots in school at the moment, so i don't think this will change.