As someone who has taken many cruises I know that in the case of norovirus if someone vomits near you then move away... far away! The virus can be spread in the micro-droplets from the vomit so it is airborne. You really don't want to be nearby. I realise that in a plane environment it is sometimes unavoidable but if someone throws up it might not be because of airsickness... they may be ill in other, more serious, more contagious ways. I treat all vomit as a biohazard!