Unless your cobalt mine in the Congo is generating billions in revenue, fending them off with modern combat aircraft is probably going to be a net loss. It's not uncommon to have maintenance costs of $10,000 or more per flight hour (the F-35 is apparently $20,000). A fleet of 46 aircraft flying, say, 8 hours per day is going to cost $110,400,000 per month at a $10,000 flight hour cost.
you won't need the full fleet to fend off any neighboring country – and as I said they offer the whole range now: from small prop-based CAS to state of the art (at least for everyone non-NATO, China or Russia) air superiority.
And I wouldn't really worry about the amount of cash available in such conflicts. In the past it generally was enough for leaders to bribe their way into being accepted citizens of the western hemisphere, see here: https://en.wikipedia.org/wiki/Isabel_dos_Santos
Now suppose, EU drops any support for the angolan government, she wants back her power: probably easy for her to start a civil war. Some neighbors (Namibia, SA) might step up (like they did in Somalia) to help the government if it holds out the initial 1,2,3 ... weeks. Normally they would have uncontested air superiority. Now Ms. dos Santos asks Mr. K.: "How about 4 of your hornets, I heard they kick ass, do you want some diamonds?" (and yeah, they can easily operate from a number of airfields there, I just counted >20 of more than 2km lengths of asphalt: https://en.wikipedia.org/wiki/List_of_airports_in_Angola). And that is how private contracting basically already works for advisors/spec-ops – great to see that extended to state-of-the-art aircraft.
Really great, good progress, all hail the capital!
Right, but now you're talking about using mercenaries to fight a civil war and vie for power over a sovereign nation. That's much higher stakes than a cobalt mine. Mercenaries in air forces have existed, but usually in the form of hiring pilots and maintenance crews to operate aircraft owned by one of the belligerent nations. This is what occurred in the Eritrean-Ethiopian war. These countries brought up former Soviet aircraft and munitions following the end of the cold war, and also hired ex-soviet pilots and ground crews to operate them. But this is a significant war with hundreds of thousands of combatants on both sides.
ahem, the DR Congo is basically in a state of civil war. And yeah, basically the air superiority is currently held by the nation state and its allies. A private force can turn this easily. Also, the soviet caches have dried up (while I doubt the demand did) and today in most conflict areas, it should be a lot easier to put a box of cash on the table to get a service than import/export a lot of stuff on your own (you need people and control for that).
