How it 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 FAA. The ADS-B, MLAT and FAA 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.

ADS-B

The primary technology that we 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.

  1. Aircraft gets its location from a GPS navigation source (satellite)
  2. The ADS-B transponder on aircraft transmits signal containing the location (and much more)
  3. ADS-B signal is picked up by a receiver connected to Flightradar24
  4. Receiver feeds data to Flightradar24
  5. Data is shown on www.flightradar24.com and in Flightradar24 apps

Today, roughly 65% of all passenger aircraft (75% in Europe, 35% in the US) are equipped with an ADS-B transponder. This percentage is steadily increasing as ADS-B is set to replace radar as the primary surveillance method for controlling aircraft.

Flightradar24 has a network of more than 4,000 ADS-B receivers around the world that receives plane and flight information from aircraft with ADS-B transponders and sends this information to our servers. Due to the high frequency used (1090 MHz) the coverage from each receiver is limited to about 250-400 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 hard to get ADS-B coverage over oceans.

About 99% of Europe is covered with ADS-B receivers. There is also good ADS-B coverage in USA, Canada, Caribbean, Brazil, Russia, Middle East, India, Japan, Thailand, Malaysia, Indonesia, Australia and New Zealand. In other parts of the world the ADS-B coverage varies.

MLAT

In some regions with coverage from several FR24-receivers we also calculate positions of aircraft with the help of Multilateration (MLAT), by using a method known as Time Difference of Arrival (TDOA). By measuring the difference in time 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. That means that MLAT coverage can only be achieved above about 10000 feet as the probability that signal can be received by four or more receivers increases with increased altitude.

Most parts of Europe are today covered with MLAT above 10000 feet. There is also some MLAT coverage in North America, Australia and Brazil. More areas will get MLAT coverage during 2014.

FAA

In addition to ADS-B and MLAT data, we also get data from the Federal Aviation Administration (FAA) in the United States. Unlike the ADS-B and MLAT data that is presented real-time, the FAA data is delayed by roughly 5 minutes due to FAA regulations. On the Flightradar24 map, all aircraft based on FAA data are orange.

FAA data is based on radar data (i.e. not just planes with ADS-B transponders) and includes most scheduled and commercial air traffic in US and Canadian air space + parts of Atlantic and Pacific Ocean.

Aircraft visible on Flightradar24 (within ADS-B coverage)

Common aircraft models that usually have an ADS-B transponder and are visible on Flightradar24 (within ADS-B coverage):

Common aircraft models that usually do not have an ADS-B transponder and are not visible on Flightradar24 (within ADS-B coverage):

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.

Aircraft visible on Flightradar24 (within MLAT or FAA coverage)

In regions with MLAT or FAA coverage most of the air traffic is visible independent of aircraft type. But as mentioned above MLAT coverage is limited to some areas with many FR24-receivers and can normally only be achieved on altitudes above about 10000 feet. Data provided by FAA is often missing aircraft registration information.

Blocking

For security and privacy reasons information about some aircraft is limited or blocked.

Coverage map

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 is different for different aircraft. If an aircraft you are looking for is not visible on Flightradar24 it either does not have correct transponder or it's out of Flightradar24 coverage.

Please visit our FAQ to find answers to frequently asked questions about Flightradar24.