What is the criteria for logging actual instrument time during flight?

When logging actual instrument time during flight, the standard is that both pilots may log the time regardless of the flight conditions. This criterion is important because actual instrument time is defined as the time spent flying in conditions that require the use of instruments for navigation and control. When two pilots are present in an aircraft under instrument conditions, they both actively participate in the flight operations, even if only one is manipulating the controls.

This logging practice allows for a more accurate representation of each pilot's exposure to and experience with instrument conditions, which is crucial for meeting training and certification requirements. The ability to log time provides valuable experience for both pilots in their instrument flight proficiency.

The other options don't align with this standard. For instance, only one pilot logging time does not accurately reflect the experience gained. Similarly, restricting logging strictly to the pilot in command or only being based on flight duration does not consider the operational involvement of multiple pilots in the cockpit during actual instrument conditions.