How Accurate Is Flight Tracking?

Flight tracking is accurate about where an aircraft was a few seconds ago, usually to within tens of metres, but the picture you see is always slightly out of date, and some information, such as arrival times, is only an estimate.

Position

ADS-B positions come from the aircraft’s GPS and are normally accurate to tens of metres. Positions calculated by MLAT can be off by hundreds of metres.

Altitude

ADS-B can transmit two altitudes: barometric (from the pressure altimeter, relative to a standard pressure) and geometric (from GPS). They can differ by hundreds of feet. Most displays show barometric altitude. See how to read altitude, speed and vertical rate.

Speed

The speed shown is usually ground speed from GPS, not the speed through the air. A tailwind makes ground speed higher. See ground speed.

Timing

Each step from the aircraft to your screen adds delay; see why flight tracking data is delayed. Many sites also move aircraft smoothly between updates by estimating from speed and heading. That is an estimate, not a new measurement.

Coverage gaps

Flights disappear where receivers do not reach. Read why flights disappear.

Arrival times

An “arrival time” on a tracker is either the airline’s estimate or a calculation from distance and speed. It can change by many minutes. See why ETA changes.

General information only, not legal or safety advice. Details change; check with your airline and the relevant authority. See our editorial policy.