Suppose I wanted to fly to Angola...

I was talking recently with someone who said that their company needs
to send a few (5-6) people to do some work in Angola from Atlanta and
complained about the difficulty of flying there commercially. This
made me curious about what it would take to do this in a private jet.
I asked my CFII this question (he is type rated for the Citation I)
and his answer was "Not in this Citation; it doesn't have the range."
He did say that a friend delivered a Citation I to South Africa solo
but it took him three days to get there. He's never personally flown
to Africa so while he said he'd look into it I thought I'd ask here as
someone might actually know.

I am going to assume that there is some sweet spot on the range-speed-
time-cost considerations based upon whatever the longest leg would
have to be for various routes and the cost/time involved with stopping
to refuel but I don't know much about this kind of aircraft, certainly
not enough to plan a trip.

I've never thought much about international flight so I am very
curious to see the suggestions for a flight like this.

TIA