Which phrase would a pilot use to confirm understanding of a new altitude assignment?

The phrase "Wilco" is used by pilots to confirm understanding of an instruction and indicate that they will comply with the request. It is a contraction of "will comply," which clearly communicates to air traffic control that the pilot has understood the altitude assignment and intends to execute it.

Using "Wilco" is a part of standard aviation communication protocol, ensuring clarity and conciseness between the pilot and air traffic controller. This minimizes the risk of misunderstanding or miscommunication, which is crucial in aviation safety.

The other phrases can imply acknowledgment but do not carry the same specific commitment to take action. For example, "Affirmative" simply confirms that the pilot understands the message but does not explicitly state that they will carry out the instruction. "Copy that" indicates receipt of the message, yet lacks the commitment to act. Meanwhile, "Roger" confirms receipt of a transmission but, similar to "Copy that," does not explicitly convey intention to follow through with the instruction.