The prudent crew will write it down. Large aircraft have tables, or boards clipped to the control column on which to write taxi clearances, complex airways clearances and so on. In some large aircraft, many light aircraft and in helicopters, pilots might wear a kneeboard to write instructions on.

Pilots remember Air Traffic Control (ATC) instructions using a system of "Short-Term Shorthand" and "Read-Back" protocols. When a controller gives a complex instruction—such as "Flight 123, climb to FL350, turn left heading 270, squawk 4521"—the pilot immediately writes this down on a "scratchpad" using standardized abbreviations (e.g., ↑350, L270, S4521). This written record acts as an external memory bank. Furthermore, the mandatory "Read-Back" serves as an auditory double-check; by repeating the instructions back to the controller, the pilot’s brain reinforces the data, and the controller can correct any misunderstandings instantly. In 2026, modern flight decks also utilize CPDLC (Controller-Pilot Data Link Communications), where instructions appear as text on a screen, allowing pilots to simply "Load" the data into the Flight Management Computer with the press of a button. This reduces the cognitive load and eliminates "read-back/hear-back" errors caused by heavy accents or radio static, ensuring that the critical "altitude, heading, and speed" data is perfectly maintained.