What is the first step to initiate communications with an aircraft?

Initiating communications with an aircraft typically begins with using the aircraft ID. The aircraft ID is a unique identifier, generally comprising the aircraft's registration number or flight number. This identification is crucial for both the controller and the pilot, as it allows for clear and unambiguous communication.

By explicitly stating the aircraft ID, the controller ensures that the intended recipient of the communication is clear, thus minimizing confusion, particularly in environments where multiple aircraft are operating simultaneously. This practice aligns with standard communication protocols in air traffic control, where clarity and precision are essential for safety and efficiency.

In contrast to other options, referencing the flight plan may provide context but does not serve as an immediate initiation of communication. Starting with a briefing focuses on procedural information rather than direct interaction, and sending a text message is not a standard or immediate method to initiate verbal communication with an aircraft. Thus, using the aircraft ID stands out as the proper first step in establishing communication.