is a period of testing or a trial journey undergone by a ship, aircraft
or other craft and its crew before being declared operational.
Statistically, a proportion of the components will fail after a
relatively short period of use, and those that survive this period can
be expected to last for a much longer, and more importantly, predictable
life-span. For example, if a bolt has a hidden flaw introduced during
manufacturing, it will not be as reliable as other bolts of the same