What is the proposed departure time on a flight plan given in?

The proposed departure time on a flight plan is given in Coordinated Universal Time (UTC), often referred to as Zulu time. This standardization is crucial for aviation as it allows for uniformity in scheduling and communication across different time zones. By using UTC, pilots, air traffic controllers, and dispatchers can coordinate flights without the complexities that arise from local time variations, such as daylight saving time changes or regional differences.

Using UTC helps eliminate confusion, especially during long flights that cross multiple time zones. It ensures that everyone involved in the flight operations is referring to the same time, facilitating smoother communication and overall flight management. This standard is recognized internationally, which is essential in a field like aviation that operates on a global scale.

The other options, while relevant in certain contexts, do not provide the same level of consistency or clarity needed for flight planning, which is why Zulu time is the preferred choice for indicating departure times.