I don't know what you have in your mind about flight doctor or aerospace doctor. Don't ever think that you would be astronauts if you become that.In other countries, flight surgeons or Doctors are nothing but the one who are working with armed forces or peace missions. They are selected by space agencies like NASA,ESA,JAXA and German Space Agency based on their talents like research, fighter jet flying skills, trecking and water sports and later some are trained as astronauts and some are trained to train astronauts for the upcoming space missions .In USA , to do aerospace medicine residency you should complete medical or surgical post graduation in their own country and you should be a citizen of it also(this is compulsory). Aerospace medicine is like super specialization there. But extremely difficult to get into because they select only armed forces Doctors and that too the spots are limited.
Ramijinni Ramji Rao M.D, M.D at Post Graduate Institute of Medical Education and Research, Chandigarh (2017-present)