For how many times is a consecutive 24-hour rest required in a 90-day period for air taxi operations?

In air taxi operations, regulations stipulate that pilots must have a certain amount of consecutive rest to ensure safety and mitigate fatigue. The requirement is for a minimum of 24 consecutive hours of rest at least once every 7 days. Over a 90-day period, which encompasses approximately 13 weeks, this translates to needing a minimum of 13 rest periods, as each week requires one consecutive 24-hour rest.

Therefore, to meet the regulatory requirements and promote safe operations, a total of 13 times is necessary during a 90-day period, making this the correct answer.