What is the final step when retracting the airstairs?

The final step when retracting the airstairs involves ensuring that the door is fully closed. This is crucial because an open door can lead to safety hazards during the aircraft's operation, including potential interference with the airstairs mechanism. Closing the door fully secures the aircraft, allowing for proper safety protocols to be followed before taxiing or taking off.

While other steps, such as detaching guard rails, pressing the STAIR OPER switch, and notifying ground control, are all important aspects of the overall process, they occur before the final action of ensuring the door is closed. The closure of the door signals that all external operations are complete, thereby confirming readiness for the next phase of the flight operation.