Definition
A cockpit unit that allows the flight crew to send and receive digital text messages between the aircraft and air traffic control or the airline's operations center, replacing some communication that would otherwise be done by voice over the radio.
Plain English
A small screen and keypad in the cockpit used to send and receive typed messages to and from controllers and the airline, instead of talking on the radio.
Context Anchor
Seen on advanced instrument panels and in discussions of cockpit safety and communication systems.
Derivation
Data link refers to a digital communication channel between two points. The unit is the device the crew uses to control that link and display the messages going through it.
Why Pilots Care
Digital messaging reduces radio congestion, eliminates many readback errors, and is the primary means of ATC communication in oceanic and remote airspace where voice contact is unreliable.
Analogy
Think of it as a dedicated cockpit message center: not a general phone or tablet, but a built-in place for important flight messages.
Intuition Check
Do not read “control” as meaning it flies the aircraft. Here, “control” means the pilot can manage the message system: view, select, accept, or respond to messages.
Example Sentence 1
After receiving the oceanic clearance on the data link control display unit, the captain reviewed it before loading it into the flight management system.
Example Sentence 2
During cruise the data link control display unit alerted the crew to an updated altitude assignment from the controller.