What should a pilot be warned of before transmitting a long message?

Before transmitting a long message, it is important for a pilot to advise when they are ready to copy. This ensures that the controller is aware that the pilot is prepared to receive extensive information, such as instructions or updates. By doing so, the communication becomes more organized, allowing for a clear and efficient exchange of information without interruptions or misunderstandings.

Being ready to copy indicates to the controller that they can now begin relaying the detailed message, which helps in managing the flow of communication effectively. It is crucial in maintaining situational awareness and ensuring that both parties are on the same page, especially during busy operations or when multiple transmissions are occurring.

The other options do not directly address the need for effective message transmission as it pertains to managing long communications. Checking the weather is important for flight safety but is unrelated to the transmission of messages. Switching frequencies may be relevant in different contexts but doesn't directly pertain to making transmissions more efficient. Repeating the last transmission is also not connected to the act of preparing for a long message.