For a flight crew, what is a significant characteristic of 'continuous duty'?

'Continuous duty' refers to a work period where flight crew members engage in duties without a legal break for rest. This characteristic is significant because it emphasizes the need for adequate rest to ensure safety and performance. Continuous duty can lead to fatigue, which is why regulations are in place that limit the duration of continuous work periods and stipulate required rest periods.

The other choices represent different aspects of flight operation and crew management. Short rest breaks between flights do not correlate with continuous duty, as they imply some level of rest is provided. Extended breaks after long flights suggest a system that allows rest, which contradicts the concept of continuous duty. Operations with multiple aircraft does not directly pertain to the definition of continuous duty, as it refers to the logistical arrangements of flights rather than the conditions of crew labor. Therefore, the emphasis on continuous work without legal rest distinctly defines the challenges and considerations that come with such duty periods.