Overall statistics for Accidents and Serious Incidents show that non revenue flights have a much higher risk of producing an accident or serious incident than the revenue flying which most professional flight crew routinely undertake. A similar, though statistically unproven conclusion may be drawn in respect of revenue flights which are planned to depart from, and return to, the same aerodrome when operated by an airline which predominantly carries out flights from one location to another. A further, also statistically unproven but highly likely, claim is often advanced that airworthiness function flights carried out by flight crew who are not trained and experienced as professional test pilots are also more likely to result in an accident or serious incident. A causal factor can be that the procedures documented within the Operations Manual and procedures implemented by an Aircraft Operator for such flights are inadequate.
Non-Standard Flights are those that are outside their normal operating experience for the operating flight crew and/or their Company.
Two issues that have usually been associated with this increased risk, either singly or together, both relate to the substantially different nature of such flights from a flight crew perspective compared to the routine of normal operations:
An unfamiliar environment with a significantly modified context for standard operating procedures, in particular the possibility in many cases of an absence of the usual en route period of relative inactivity.
The apparent willingness of a minority of flight crew making non-standard flights to apply less than their usual rigor to the use of prevailing standard operating procedures. A well-knit flight test team, including the right spirit and motivation, is much more important for operational safety than a well-trained pilot on their own.