I agree also that one guy could do it, but a "co-conspiritor" would make the job dead easy...
Also, as mentioned previously, there had to be someone on the inside, as the $$$$'s owed go to different places...the gov't, fueller, ATC, local militia and anyone else with a hand to put out...
I have been on the crew of one repo from Guam (which ended up in Luanda-anyone remember N118CL?) and have been the Capt on 2 others from Eastern Europe.
I wasn't privvy to the details of the 1st one, but the 2 I took out of XXXXXX all I had to do was grease the ATC and Aerodrome folks, and the local police...
As anyone knows, the radar is minimal at best along the west coast of Africa, and there are many places to land, and if the money man is in one of those countries, you can bet the wheels were greased to make the arrival smooth...