What should a pilot do before sending a complicated message?

Before sending a complicated message, it is essential for a pilot to advise Air Traffic Control (ATC) that they are ready to copy. This communication step is crucial because it ensures that ATC is prepared to receive and accurately document the detailed information that will follow. By indicating readiness, the pilot helps establish an effective exchange where both parties can focus on the content of the message without distraction.

If ATC knows that the pilot is ready to transmit important information, they can allocate the necessary attention to accurately understand and record that information. This communication practice supports overall operational efficiency and safety by minimizing miscommunication or confusion that could arise from unexpected or rushed transmissions.

The other options, while they may have their contexts, do not address the need for clarity and readiness during the transmission of complex messages. For instance, notifying ground crew, switching to a private frequency, or aborting the transmission would not adequately ensure that ATC is prepared to handle the information that the pilot is about to convey.