What is the initial action to take if the captain becomes unresponsive during a flight at FL350?

In the scenario where the captain becomes unresponsive at FL350, the most critical initial action is to attempt to wake the captain. This immediate response is essential for several reasons. First, the safety and well-being of all onboard depend on ensuring that the flight crew is properly functioning and able to control the aircraft. Attempting to wake the captain allows the other crew members to assess whether the captain is incapacitated due to a medical emergency, such as a hypoxia or other health issues.

While putting on an oxygen mask is important in case of cabin altitude issues, or putting the captain's oxygen mask on may be necessary if you confirm they are incapacitated, the priority must be to ascertain consciousness and responsiveness. If the captain can be roused, the flight can continue with minimal disruption. If they are unresponsive and incapacitated, then following through with emergency protocols, including declaring an emergency and possibly diverting, becomes the next logical step.

Thus, the action of attempting to wake the captain directly influences subsequent actions and helps determine the appropriate course of action for the safety of the passengers and crew.