What signal indicates "ready for taxi" right before closing the flight deck door?

The signal indicating "ready for taxi" right before closing the flight deck door is a thumbs up. This gesture is widely recognized in aviation as a clear and concise way to communicate readiness without the potential for misinterpretation that verbal commands might carry, especially in a noisy environment. The thumbs up is visible from a distance, ensuring that ground crew and pilots can effectively communicate without needing to rely on words.

In the aviation context, using hand signals like the thumbs up minimizes the risk of misunderstandings, which is crucial during critical phases of flight preparation. The gesture is simple enough for everyone involved to understand quickly, allowing for a more efficient workflow in the busy pre-flight environment.