With the decline in air traffic around the world, the visibility of certain flights has attracted attention and we’ve received quite a few questions. We’ve provided answers to common questions below. If you have a question we didn’t answer, please let us know in the comments or you can reach us on Twitter or Facebook.

Survey patterns

One of the most visible quirks of flying at the moment are survey-pattern flights. These flights take place all the time for a variety of reasons. Some flights are capturing imagery for mapping services—‘satellite’ maps used in commercial mapping services are often partially compiled from aerial imagery. Other flights are completing various other surveys using technology like LiDAR. Some of these are working on ecological projects, engineering works, or even checking for leaks in utility pipes.

Ground vehicles

We’re a flight tracker, but we also track airport ground vehicles that are equipped with transponders. Transponder-equipped ground vehicles enhance safety on the airfield by ensuring the vehicles can be seen by air traffic control and other vehicles and aircraft. Ground vehicles visible on Flightradar24 are generally those that are most active in the movement areas of an airport, like airport rescue and fire fighting, ‘follow me’ cars, and push back tugs. At some airports, specialized vehicles like wildlife control and lawnmowers are visible.

Incorrect or missing route display

‘Is that plane really going to…’ is a question we often receive when the route listed doesn’t match the current location or track of the aircraft. The route of the flight is not received directly from the aircraft. Through the use of various schedule databases and what some might call machine learning, but we’ll just call computer magic, we match the call sign the aircraft is broadcasting to a flight number and route for that flight. Sometimes the computer matches the flight incorrectly and sometimes it isn’t matched at all.

A route can be matched incorrectly for a few reasons, but generally it is because the flight is using the same call sign for a flight that previously flew the listed route and we have no received a schedule update for the current flight. For example, Turkish Cargo flight 6492 has flown between Istanbul and Riyadh multiple times recently and been matched correctly, but the airline also uses the flight number for other flights including Istanbul-Entebbe. Because we’re not receiving a schedule update from one of our schedule providers, the flight is incorrectly matched in this case. Schedule matching issues are more likely for cargo or special flights as they may not file a commercial schedule update or the routing is changed at the last minute after we have matched a flight to a route.

I heard a plane, but I don’t see it on Flightradar24

A flight may not be visible on Flightradar24 for different reasons, but most likely it is either outside our coverage in that area or not equipped with a compatible transponder or a combination of the two. Our service operates via line-of-sight radio signals and if receivers in the area are unable to see the aircraft, it cannot be displayed. For some aircraft operating with an older transponder, it is necessary for multiple receivers to see the aircraft in order to display it. That technology is called Multilateration (MLAT), which we’ve written about extensively before.

Restricted aircraft

Operators of private or sensitive aircraft may request their tracking details be restricted or not displayed. Generally, aircraft requesting that they not be displayed on Flightradar24 are military aircraft. Some military aircraft, such as various transport aircraft, are visible.