How flight tracking works
Flightradar24 is a flight tracker that shows live air traffic from around the world. Flightradar24 combines data from several data sources including ADS-B, MLAT and radar data. The ADS-B, MLAT and radar data is aggregated together with schedule and flight status data from airlines and airports to create a unique flight tracking experience on www.flightradar24.com and in Flightradar24 apps.
The primary technology that Flightradar24 use to receive flight information is called automatic dependent surveillance-broadcast (ADS-B). The ADS-B technology itself is best explained by the image to the right.
- Aircraft gets its location from a GPS navigation source (satellite)
- The ADS-B transponder on aircraft transmits signal containing the location (and much more)
- ADS-B signal is picked up by a receiver connected to Flightradar24
- Receiver feeds data to Flightradar24
- Data is shown on www.flightradar24.com and in Flightradar24 apps
ADS-B is a relatively new technology under development, which means that today it's rarely used by Air Traffic Control (ATC). Our estimations show that roughly 70% of all commercial passenger aircraft (80% in Europe, 60% in the US) are equipped with an ADS-B transponder. For general aviation this number is probably below 20%. The percentage of aircraft equipped with ADS-B receivers is steadily increasing though, as they will become mandatory for most aircraft around the world by 2020. When mandatory, ADS-B will replace primary radar as the primary surveillance method used by ATC.
Flightradar24 has a network of more than 20,000 ADS-B receivers around the world that receive flight information from aircraft with ADS-B transponders and send this information to our servers. Due to the high frequency used (1090 MHz) the coverage from each receiver is limited to about 250-450 km (150-250 miles) in all directions depending on location. The farther away from the receiver an aircraft is flying, the higher it must fly to be covered by the receiver. The distance limit makes it very difficult to get ADS-B coverage over oceans.
On cruising altitude (above 30,000 feet) Flightradar24 covers 100% of Europe and of the USA. There is also good ADS-B coverage in Canada, Mexico, Caribbean, Venezuela, Colombia, Ecuador, Peru, Brazil, South Africa, Russia, Middle East, Pakistan, India, China, Taiwan, Japan, Thailand, Malaysia, Indonesia, Australia and New Zealand. In other parts of the world the ADS-B coverage varies. We are continually adding coverage all over the world via our FR24-receivers.
In some regions with coverage from several FR24-receivers we also calculate positions of non-ADS-B equipped aircraft with the help of Multilateration (MLAT), by using a method known as Time Difference of Arrival (TDOA). By measuring the time it takes to receive the signal from aircraft with an older ModeS-transponder, it's possible to calculate the position of these aircraft. Four FR24-receivers or more, receiving signals from the same aircraft, are needed to make MLAT work. MLAT coverage can only be achieved above about 3,000-10,000 feet as the probability that four or more receivers can receive the transponder signal increases with increased altitude.
Most parts of Europe and North America are today covered with MLAT above about 3,000-10,000 feet. There is also some MLAT coverage in Mexico, Brazil, South Africa, India, China, Japan, Taiwan, Thailand, Malaysia, Indonesia, Australia and New Zealand. More areas will get MLAT coverage as we continue to add new receivers to our network.
Satellite-based flight tracking is the latest step in our quest for global ADS-B coverage. Satellites equipped with ADS-B receivers collect data from aircraft outside our terrestrial ADS-B network’s coverage area and send that data to the Flightradar24 network. Satellite-based ADS-B data available on Flightradar24 comes from multiple providers. As the number of satellites supplying data and their location are dynamic, satellite coverage varies. Generally, satellite-based ADS-B increases coverage of flights over the ocean where ground-based reception is not possible. Only aircraft equipped with an ADS-B transponder may be tracked via satellite.
North America Radar Data
In addition to ADS-B and MLAT, we also receive additional live data for flights in the North America. This data is based on radar data (not just aircraft equipped with ADS-B transponders) and includes most scheduled and commercial air traffic in the US and Canadian airspace, as well as parts of the Atlantic and Pacific Ocean.
Flarm is simpler version of ADS-B with a shorter range, primary used by smaller aircraft, in most cases gliders. The range of a Flarm receiver is between 20 and 100 km. Flarm receivers are often installed on small airports with a lot glider traffic to track the gliders around the airport. Read more about Flarm on Wikipedia
When an aircraft is flying out of coverage Flightradar24 keeps estimating the position of the aircraft for up to 2 hours if the destination of the flight is known. For aircraft without known destination, position is estimated for up to 10 minutes. The position is calculated based on many different parameters and in most cases it's quite accurate, but for long flights the position can in worst cases be up to about 100 km (55 miles) off. In settings there is an option to set for how long time you want to see estimated aircraft on map.
Aircraft visible on Flightradar24 (within ADS-B coverage)
When ADS-B was initially launched, it was primarily used in commercial passenger aircraft with 100+ passengers. An increasing number of aircraft including smaller aircraft types, are getting ADS-B transponders but, until ADS-B becomes mandatory it's up to the aircraft producer and owner to decide if an ADS-B transponder should be installed or not.
Common aircraft models that usually have an ADS-B transponder and are visible on Flightradar24 (within ADS-B coverage):
- All Airbus models (A300, A310, A318, A319, A320, A321, A330, A340, A350, A380)
- Antonov An-148 and An-158
- ATR 72-600 (most new deliveries)
- BAe ATP
- BAe Avro RJ70, RJ85, RJ100
- Boeing 737, 747, 757, 767, 777, 787
- Bombardier CRJ-900 (most new deliveries)
- Bombardier CS100 and CS300
- Embraer E190 (most new deliveries)
- Fokker 70 and 100
- McDonnell Douglas DC-10 and MD-11
- Sukhoi SuperJet 100
- Some newer Ilyushin and Tupolev (for example Il-96 and TU-204)
Common aircraft models that usually do not have an ADS-B transponder and are not visible on Flightradar24 (within ADS-B coverage):
- Antonov An-124 and An-225
- ATR 42, 72 (except most new deliveries of ATR 72-600)
- Boeing 707, 717, 727, 737-200, 747-100, 747-200, 747SP
- BAe Jetstream 31 and 32
- All Bombardier CRJ models (except most new deliveries of CRJ-900)
- All Bombardier Dash models
- All CASA models
- All Dornier models
- All Embraer models (except most new deliveries of Embraer E190)
- De Havilland Canada DHC-6 Twin Otter
- Fokker 50
- McDonnell Douglas DC-9, MD-8x, MD-90
- Saab 340 and 2000
- Most helicopters
- Most older aircraft
- Most business jets
- Most military aircraft
- Most propeller aircraft
Of course there are lots of exceptions from these rules. There are some older A300, A310, A320, B737, B747, B757, B767, MD10, MD11 aircraft flying without an ADS-B transponder, which make those aircraft invisible on Flightradar24 when in areas with ADS-B coverage only. But there are also some Twin Otters, Saab 340, Saab 2000 and MD-80 aircraft with an ADS-B transponder that are visible on Flightradar24 in areas with ADS-B coverage.
Aircraft visible on Flightradar24 (within MLAT, radar, or Flarm coverage)
In regions with MLAT, radar, or Flarm coverage most of the air traffic is tracked and visible independent of aircraft type. That includes propeller aircraft, helicopters and gliders. But as mentioned above, MLAT coverage is limited to some areas with many FR24 receivers and can normally only be achieved at altitudes above about 3,000-10,000 feet, which means that general aviation at lower altitudes may be flying below MLAT coverage. North American radar data in most cases does not include general aviation flights without a flight plan. Radar data is often missing aircraft registration information and aircraft tracked with MLAT in many cases are missing the callsign information.
For security and privacy reasons information about some aircraft is limited or blocked. This includes most military aircraft and certain high profile aircraft, like Air Force One.
In areas where Flightradar24 normally have coverage, all major airports are marked with blue airport markers.
Flightradar24 relies on volunteers around the world for the majority of our coverage. Find out how you can contribute and host a receiver.
Please note that coverage and aircraft visibility is dependent of many parameters including aircraft type, aircraft transponder type, aircraft altitude and terrain, so coverage can be different for different aircraft, even on the same location. If an aircraft you are looking for is not visible on Flightradar24 it either does not have a compatible transponder or it's out of Flightradar24 coverage.
Please visit our FAQ to find answers to frequently asked questions about Flightradar24.