If a pilot is incapacitated but breathing, what is the first action a crew member should take?

In the scenario where a pilot is incapacitated but still breathing, the immediate priority for the crew member is to ensure that the environment is safe and that the incapacitated pilot can receive necessary assistance. This is why considering the use of the O2 bottle is a critical first action. If the pilot is incapacitated and not responding, there may be a need for supplemental oxygen, especially if the cause of the incapacitation could affect their breathing or if there is any doubt about the cabin environment or altitude.

Using the O2 bottle ensures that the pilot continues to receive oxygen, which is vital for maintaining their respiratory function and potentially stabilizing their condition until more definitive care or support can be provided. This action is a proactive measure to safeguard the pilot’s health and will provide the crew member time to assess the situation further and make additional decisions.

The other actions listed may indeed be necessary, such as passing control to another pilot or engaging safety measures like the inertial reel lock, but they come after ensuring that the incapacitated pilot's immediate oxygen needs are addressed. Commencing CPR is only warranted if the pilot is not breathing at all, which is not the case here. Thus, considering the O2 bottle as the first response is the most logical and appropriate