In the checklist for an engine fire in flight, what is the first action to be taken?

The first action to be taken in the event of an engine fire in flight is to set the mixture to Idle Cut-Off (ICO). This action is crucial because it effectively stops the flow of fuel to the engine, which is essential in preventing further combustion and minimizing the risk of an explosion or extensive fire damage. By cutting off fuel supply, the pilot is addressing the immediate threat of fire, thereby enhancing the chances of regaining control over the situation.

While maintaining an appropriate speed, notifying air traffic control, and performing a controlled descent are important components of overall emergency management, they should follow the immediate action of cutting off the fuel supply. The priority in such emergencies is to mitigate the fire at its source, making the adjustment of the mixture the first and most critical step.