Definition
FIS-B is a free, ground-based broadcast service delivered over the 978 MHz UAT data link as part of the ADS-B system. It transmits aeronautical and meteorological information — including weather radar imagery, METARs, TAFs, PIREPs, AIRMETs, SIGMETs, NOTAMs, TFRs, winds and temperatures aloft, and special use airspace status — to properly equipped aircraft in flight.
Plain English
FIS-B is a free service that beams weather and flight information up to your cockpit while you fly, as long as you have the right receiver on board.
Context Anchor
You may see FIS-B mentioned when using an in-flight weather display, portable receiver, or aircraft system that receives broadcast flight information.
Derivation
The name describes its function: it provides Flight Information as a Broadcast (one-way transmission from ground to aircraft, like a radio station). 'Broadcast' signals that the data is sent out continuously to anyone equipped to receive it — you don't request it, you just tune in.
Why Pilots Care
It gives pilots real-time access to weather and advisories without voice requests, supporting better enroute decisions and safety.
Analogy
It is like a radio station for flight information: the station sends the information out, and your equipment receives it if you are in range and tuned to the right system.
Intuition Check
Do not assume FIS-B is a two-way request service or a guarantee that every item is complete and current. It is a one-way broadcast of selected information to equipped aircraft.
Example Sentence 1
Before descending into the valley, the pilot checked the FIS-B weather display and saw a fresh AIRMET for mountain obscuration.
Example Sentence 2
FIS-B delivered the updated NOTAMs to the cockpit display during the cross-country flight.