What should be done immediately by FA 1 upon discovering a fire?

The immediate action that FA 1 should take upon discovering a fire is to obtain a fire extinguisher and protective breathing equipment. This is crucial because addressing the fire as quickly and safely as possible can prevent it from spreading and potentially causing greater harm. The fire extinguisher is essential for attempting to put out the fire, while protective breathing equipment is necessary to ensure that the flight attendant can breathe safely if smoke is present.

Timely access to these resources allows for a more effective response to the emergency, giving FA 1 the tools needed to manage the situation before it escalates. The focus here is on tackling the fire while ensuring the safety of the crew and passengers; hence, having the right equipment on hand is paramount.

While investigating the fire's source, alerting passengers, and turning off the air conditioning system may be appropriate steps following the immediate acquisition of necessary equipment, they do not address the critical first response of attempting to control the fire itself. Ensuring appropriate response is aligned with emergency protocols prioritizes life safety over other actions that can impede a timely response to a developing emergency.