I see this issue has also been aired on other threads so my take on it:
the good news is that if you take retovirals before exposure or within an hour of exposure you do not get infected - there is pressure to provide this prophylaxis called PREP in the UK but it is up to politicians not scientists so expect the usual incompetence.
Even if you become infected retrovirals, taken for life, should give you a normal lifespan without medical issues
but here comes the problem for the regulator. Most people who have HIV didnt take PREP initially. They were infected for a period before they received treatment. The possibility exists that they may have developed some problems or may develop them in the near future.
In addition there is a risk the individual may stop their retrovirals. In the US less than half HIV positive people take them due to cost. Pilots may run out especially if flying long haul. etc etc
And all these risks can not only result in incapacitation but worse mental health issues including psychosis. This can lead to untruthful medical declarations etc etc.
It is an impossible position unfair on some pilots.The irony is that we should have eradicated new cases. If 95% of those who are HIV positive took retrovirals the epidemic would end but in the UK we fail to test enough people (those we test positive we do treat) and in the US they test enough but far too few take retrovirals. An epidemic the scientists can stop but the politicians cant.....