What is ADS-B? The Tech Behind Modern Flight Tracking

ADS-B in one sentence

Every modern aircraft constantly broadcasts its position, altitude, speed, identity, and intent — and anyone with a $30 receiver can listen.

The acronym

Automatic Dependent Surveillance–Broadcast.

• Automatic: the aircraft does it without being asked.
• Dependent: the aircraft relies on its own GPS.
• Surveillance: ATC and others can watch.
• Broadcast: sent omnidirectionally on 1090 MHz (or 978 MHz UAT in the US for general aviation).

What gets transmitted

• Position (lat/lon)
• Altitude
• Velocity (speed and direction)
• ICAO 24-bit address (unique per aircraft)
• Call sign
• Squawk code
• Some intent data (target altitude, navigation info)

Updated once or twice per second.

Why it changed everything

Before ADS-B, ATC relied on rotating radar (one update per ~6 seconds) and aircraft were invisible over oceans. ADS-B made:

• Real-time consumer flight tracking possible.
• Reduced separation in oceanic airspace, saving fuel.
• Search and rescue dramatically faster.

Coverage

• Land: excellent globally.
• Coastal water: good thanks to ground-station overlap.
• Open ocean: covered by satellite ADS-B (Aireon constellation since 2018).
• Polar: improving.

Limitations

• ADS-B is unencrypted. Anyone can receive it.
• Some military and high-profile private aircraft block public display via PIA/LADD programs.
• A small number of aircraft still don't transmit ADS-B Out (mostly older GA).

How modern apps use it

A flight tracker like FlightyFlow blends ADS-B from worldwide receivers with airline operational feeds, weather radar, and FAA data to deliver predictive trip insight in addition to a live position.