What ACARS really is
Every airliner is sending and receiving digital messages for its entire flight, and across the world it adds up to tens of thousands every hour. That traffic is ACARS, a datalink running since 1978 over VHF radio, HF radio, and satellite. It is the layer that turns a plane from a silent dot into something you can actually follow.
A little of it is routine. The rest is the good stuff: a flight declaring an emergency, a diversion being worked out in the air, an engine the crew is nursing, a medical onboard, the blunt back and forth between the cockpit and the ground. When something happens up there, ACARS is usually where the real reason shows up first, before the airline says a word and before it reaches the news.
Why read ACARS in Flight Deck
Catching these messages yourself means a radio, an antenna, and only the aircraft passing over your roof. Flight Deck does it at a completely different scale.
- The whole planet. We pull ACARS from across the world, not just whatever flies near one antenna. You are never limited to your own patch of sky.
- The reason behind the drama. When a flight diverts or declares, the why often lands here in real time, decoded into plain words.
- Signal, not noise. Tens of thousands of messages an hour, filtered down to the handful actually worth seeing.
- Be first. The interesting moments surface the instant they happen, so you can know before almost anyone.
How to read ACARS messages
There are two paths. The hobbyist path is to receive ACARS yourself with a software-defined radio and a decoder, then read the raw messages as they land. It works, and it is a fun rabbit hole, but it means antennas, dongles, and a lot of shorthand.
The faster path is Flight Deck. Open it, tap a plane, and the live ACARS feed is right there, decoded and sitting next to the flight on a map, with an alert when something worth noticing comes through. No radio required.
ACARS vs ADS-B
These two get confused a lot. ADS-B is how an aircraft broadcasts its position, and it is what powers the dots on a tracking map. ACARS is how the aircraft sends messages. One answers where a plane is. The other answers what is being said on board. Flight Deck shows you both at the same time.
ACARS FAQ
What does ACARS stand for?
ACARS stands for Aircraft Communications Addressing and Reporting System. It is a digital datalink that lets aircraft and airline ground stations trade short text messages over VHF radio, HF radio, and satellite.
What information do ACARS messages contain?
Far more than gate times. ACARS carries emergencies and diversions, weather, fuel and engine data, maintenance faults, and free text between the crew and the airline. Some of it is a routine status ping. Some of it is the real reason a flight just turned around, sent in real time.
How do I read ACARS messages?
Two ways. You can receive ACARS yourself with a software-defined radio and a decoder, then read the raw output. Or you can open Flight Deck, tap a flight, and read the decoded feed without any hardware.
Is it legal to receive ACARS?
Listening to ACARS for personal use is allowed in most countries, including the United States. Rules on recording or rebroadcasting what you receive vary by country, so check your local regulations. Flight Deck only shows data that is already broadcast in the open.
What is the difference between ACARS and ADS-B?
ADS-B is a position broadcast and powers the moving dots on a tracking map. ACARS is a messaging system and carries the text the crew and airline send each other. One tells you where a plane is. The other tells you what is being said on board.
Can I read ACARS on my phone?
Yes. Flight Deck is an iPhone app that decodes live ACARS for any flight, with no radio gear required.
Keep reading
Read live ACARS on your iPhone
Tap a plane and see the real messages from the cockpit, decoded for you. Free on the App Store.
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