Which situation does NOT require a KIO call in ET?

In the context of formation flying, a KIO (Knock It Off) call is employed to terminate an exercise or maneuver due to safety concerns or potential issues within the formation. The purpose of a KIO call is to ensure the safety of all aircraft involved.

Maintaining altitude is a stable situation that does not present immediate danger or conflict within the formation. It indicates that the aircraft is operating as expected and maintaining controlled flight, which does not necessitate a KIO call. This is crucial for ensuring that all pilots can focus on maintaining formation integrity without unnecessary alarms or interruptions.

In contrast, busting the 3/9 line, violating the 300 ft. safety bubble, and dropping below 100 KIAS are all situations that can compromise safety during formation flying, as they may lead to potential collisions or loss of control. Each of these scenarios requires immediate attention and a KIO call to halt operations and address the unsafe conditions. Maintaining altitude represents a situation where everything is functioning correctly, allowing for a continuation of the flight without the need for a KIO call.