3 mins in a radar environment could be anything from 15 to 20 nm. Enough for said environment. In a procedural environment 10min are required.
Flight levels are hotly contested in Africa and being a non-RVSM environment the chap from the "major international airline" didnt want to sacrifice 4000' which in his mind were HIS.!!
Jay Jay, did their routes converge from there on?? If not, It wouldnt have been too much of a hassle climbing back up to the previous cruising level. If they were to stay on same tracks, then it would be bad luck. This chap should understand that he is not the only one out there. Very unproffesional indeed.
Maybe too much reliance on TCAS and his own abilities to provide ATC on 126,9 !!
You gonna tell us which "major international airline" it was??