Final answer:
The number of flight attendants that can be on crew rest at a time is determined by aviation regulations and airline policies, which depend on the flight duration.
Step-by-step explanation:
The question of how many flight attendants can be on crew rest at a time typically falls under the aviation regulations, which is dependent on the duration of the flight and airline policies. This is part of the operational aspect of airline management, which ensures that crew members, including flight attendants, get the required rest during long-haul flights for safety and performance reasons.
These rules can be governed by international regulatory bodies, such as the International Civil Aviation Organization (ICAO), as well as national aviation authorities.
For instance, on a long-haul flight, the regulation may require a minimum number of flight attendants to be on duty, and this would indirectly determine how many can be on rest simultaneously. An airline's operations manual will typically specify the details, including crew rest periods and staffing requirements.
However, it's important to note that your question refers to cruise ships in the Caribbean, which is unrelated to the topic of flight attendants and crew rest. Major cruise lines operate with a different set of regulations and do not involve flight attendants or airline staff onboard. It is also noted that major cruise lines do not operate in the Caribbean during hurricane season.