What is the response when a flight crew member signals they are ready for taxi?

The correct response when a flight crew member signals they are ready for taxi is a thumbs up. This visual signal is clear and universally recognized within aviation to indicate readiness and cooperation. It allows for quick communication between the flight crew and ground personnel, minimizing the potential for misunderstandings that could arise from verbal signals, especially in noisy environments.

A thumbs up is also a signal that can be seen easily from a distance, making it effective in busy airport scenarios where multiple aircraft might be moving or where clear visual confirmation is necessary. This gesture plays a crucial role in maintaining safety and operational efficiency on the tarmac.

In contrast, other options like a button press, shouting readiness, or a head shake would not serve as effective communication methods during the taxi phase. A button press could relate to an onboard system but lacks the visual clarity needed externally between crew members and ground staff. Shouting is impractical due to potential noise interference, and a head shake is generally a sign of negation rather than confirmation of readiness, making it inappropriate in this context.