Definition
A longer, automatic broadcast transmitted by a Mode S transponder that includes the aircraft's identity, position, altitude, velocity, and other status data. It is the data format used by ADS-B Out (1090ES) to broadcast aircraft information to ATC ground stations and other aircraft once per second without being interrogated.
Plain English
A continuous radio message your transponder sends out by itself, telling everyone where you are, how high you are, and how fast you're going. It happens automatically, about once a second, even if no one asks for it.
Context Anchor
Seen in flight plan equipment codes, transponder equipment descriptions, and ADS-B Out discussions.
Derivation
Squitter' was coined by radar engineers to describe a short, spontaneous transponder transmission sent without being interrogated -- a blend suggesting a quick, unprompted 'squirt' of data. 'Extended' means the message is longer than the original squitter, carrying enough room for position, velocity, and identity data rather than just a basic reply.
Why Pilots Care
Provides continuous aircraft tracking for controllers and traffic awareness without radar, supporting safer navigation and separation in instrument airspace.
Analogy
It is like your aircraft periodically announcing, “Here I am, this is who I am, and this is where I’m going,” instead of waiting for someone to ask.
Intuition Check
Do not read “extended” as meaning longer radio range. Here it means the transponder message itself carries extra information.
Example Sentence 1
The aircraft is equipped with a 1090ES extended squitter transponder, satisfying the ADS-B Out requirement.
Example Sentence 2
Equipment code entry confirmed extended squitter capability during flight plan filing for the instrument procedure.