Under what circumstance are flight attendants not required to attend the crew member briefing?

Flight attendants are not required to attend the crew member briefing when one flight attendant is meeting operational needs on the aircraft. This situation recognizes the practical necessity of maintaining operations and ensuring the safety and readiness of the aircraft and its passengers. When an attendant is actively involved in tasks essential for operational efficiency—such as preparing the cabin, attending to passenger needs, or ensuring that safety protocols are being followed—they may be excused from the briefing.

This is an operational decision that balances the need for proper briefing with the immediate requirements of maintaining a safe and functional environment on the flight. The remaining options do not present circumstances that prioritize operational needs in the same way; sickness, flight delays, and cancellations all imply scenarios where the flight attendant's presence in briefings would still be required or could be covered by other crew members.