Which alert signifies that an aircraft is experiencing difficulty?

The correct answer signifies a situation where an aircraft is experiencing difficulty that may lead to an emergency landing or a critical situation requiring immediate assistance. Alert 2 is specifically used in aviation terminology to indicate that an aircraft is in distress but has not yet declared an emergency. This alert system is important for coordinating emergency response efforts and ensuring that fire and rescue services are prepared for potential scenarios.

Alert levels escalate based on the severity of the situation: Alert 1 typically indicates that an aircraft is on a routine flight with no issues, while Alert 3 and Alert 4 indicate more severe situations, such as a confirmed emergency or crash. The clear delineation of these alerts allows emergency services to allocate resources and respond appropriately, with Alert 2 serving as a crucial signal that indicates the aircraft's situation is serious but not yet beyond recovery.