When is number 2 allowed to respond with "2" during a flight?

Number 2 is allowed to respond with "2" when immediately responding to an in-flight directive because this succinct acknowledgment allows for clear and efficient communication within the formation. This response indicates that number 2 has received and understood the command given by the flight lead or any relevant communication that requires a prompt acknowledgment.

In a formation flying context, maintaining precise and timely communication is crucial for safety and effectiveness. The use of "2" serves to confirm that number 2 is ready to comply with instructions without adding unnecessary words that could clutter radio frequency, especially in high-pressure situations where clarity is vital.

In contrast, responding during casual conversation, spotting another aircraft, or preparing for landing may not be immediate directives requiring acknowledgment, and thus, may lead to misunderstandings or delays in communication that the flight does not want during critical moments.