What must happen if a passenger stands up during taxi?

When a passenger stands up during taxi, the correct response is that the aircraft must remain stopped. This is a safety protocol designed to ensure the safety of all on board, as passengers standing can pose a risk to themselves and others during the critical phase of taxiing when the aircraft is moving on the ground. Keeping the aircraft stationary allows the crew to address the situation properly, ensuring that the passenger is seated and secured before the aircraft resumes taxiing.

This procedure is essential in preventing accidents or injuries that could occur from sudden movements of the aircraft or if the passenger were to lose their balance. By stopping the aircraft, the flight crew can focus on ensuring that all passengers are compliant with safety regulations, thus promoting a safer flight environment.