 To some extent, these numbers had been deemed acceptable, as it was understood that the very nature of air ambulance operations meant that, because a life was at stake, air ambulances would often operate on the very edge of their safety envelopes, going on missions in conditions where no other civilian pilot would fly.As a result, nearly fifty per cent of all EMS personnel deaths in the United States occur in air ambulance crashes.In 2006, the United States National Transportation Safety Board (NTSB) concluded that many air ambulances crashes were avoidable, eventually leading to the improvement of government standards and CAMTS accreditation.