For a flight time of 10 hours 31 minutes, how many hours of rest are required for on-demand operations?

In on-demand operations under Part 135 regulations, the amount of required rest for pilots is directly influenced by their flight time. For a flight duration that exceeds 10 hours, the regulations stipulate that pilots must have a minimum of 12 hours of rest before they are eligible for their next flight duty.

Flight time is cumulative, meaning any period of flying contributes to the total time, and because 10 hours and 31 minutes is above the 10-hour threshold, pilots must adhere to the 12-hour rest requirement to ensure they are well-rested and fit for duty. This approach is in place to mitigate fatigue, ultimately enhancing safety and operational efficiency.

The options suggesting less than 12 hours do not meet the regulatory requirements, specifically designed to accommodate the pilots' need for recovery after extended flight duties. Thus, the proper rest duration after a flight time of 10 hours 31 minutes is indeed 12 hours.