Definition
A specific text-based communication capability that allows pilots and air traffic controllers to exchange clearances, requests, and reports as digital messages instead of voice radio calls. It uses the FANS 1/A standard (the original data-link protocol developed for oceanic and remote operations) and routes the messages through the Iridium satellite network, which provides global coverage including the polar regions. An aircraft equipped with this capability can be assigned routes and procedures that require data-link communications, such as certain RNAV departures and oceanic tracks.
Plain English
A way for the pilot and controller to send each other typed messages through satellites instead of talking on the radio. The system uses a worldwide satellite network that even covers the poles, so it works almost anywhere on Earth.
Context Anchor
Seen in aircraft capability listings, flight plan equipment entries, and procedures or airspace where data-link communication may be required or preferred, especially where normal radio coverage is limited.
Derivation
CPDLC stands for Controller-Pilot Data Link Communications -- a direct description of the function. FANS (Future Air Navigation System) was a 1980s ICAO concept for modernizing how aircraft and ATC communicate over oceans and remote areas; '1/A' identifies the first operational version of that standard. SATCOM is short for satellite communications. Iridium is the name of the satellite network used (named after the element iridium, atomic number 77, originally because the network was planned to use 77 satellites). Knowing the pieces helps because the term is really four labels stacked together: what the system does, which standard it follows, how the signal travels, and which satellite network carries it.
Why Pilots Care
Provides reliable two-way text communication beyond VHF radio range, reduces frequency congestion, and supports more precise route and altitude clearances.
Analogy
It is similar to sending a secure text message to air traffic control through a satellite connection, rather than talking by voice over a radio.
Intuition Check
Do not read this as a navigation system by itself. It is a communication capability: it helps pilots and controllers exchange messages, but it does not steer the airplane or define the route.
Example Sentence 1
The flight plan was filed with CPDLC FANS 1/A SATCOM (Iridium) listed in the equipment field, which qualified the aircraft for the polar route clearance.
Example Sentence 2
During the RNAV departure, ATC issued a revised clearance via CPDLC FANS 1/A SATCOM (Iridium) instead of voice.