Ah the joys of the Botswana work permit application process *headdesk*
Any job openings must be advertised for a minimum of 14 days during which only citizens can apply, then non citizens can apply after those two weeks. Or something like that.
Usually a job advert means someone has already been hired and the ad is written to suit the person. Case in point for the recent Kavango ad- they just took a couple of guys. My guess is Mack Air are just trying to expedite the application process for anyone they take for the rest of this year, and for pilots wanting to renew contracts (Note the December closing date!).
It's certainly an unusual process, advertising after you hire. I've seen people apply for advertised jobs and wonder why they didn't get so much as an email back. But this is Africa and we all love it here.