many of them insist on two pilots when it comes to commercial operations. Two CPL or ATPL holders that is. That, however, is the national CAAs, not the certification agency. For example, AIUI, all public transport jet ops require two pilots, Europe and the USA. Funnily enough, doing the same PT op in a turboprop (a twin TP, or a SE TP where this is legal e.g. the USA) requires just one pilot....