Once an engine has started at the gate, what is the next step if the aircraft has an inoperable APU and requires an airstart?

In the scenario where an aircraft has an inoperable Auxiliary Power Unit (APU) and requires an airstart after the engine has started at the gate, it's critical to wait for clearance from the captain. The captain is responsible for the overall safety and operation of the aircraft, and their clearance is essential before proceeding with any further actions.

This step ensures that all safety protocols are adhered to, and that the captain has a complete understanding of the situation before continuing with the airstart procedure. The decision to conduct an airstart requires coordination with multiple parties, and the captain's approval is necessary to ensure that conditions are safe and that all required procedures are being followed. This helps avoid any miscommunication and enhances safety during operations.

Other options may involve consideration of safety checks or informing ground control, but these actions would typically follow the captain's direction in such a scenario, emphasizing the importance of following the chain of command in aviation operations.