The altitude that got lost on the way
An aircraft with an ADS-B transponder sends its position roughly twice a second, and the altitude travels in the very same message. So when 17,000 positions don’t carry a single altitude, the aircraft are not the ones keeping quiet. It gets lost somewhere on the way.
The way leads through a box in the owner’s home: the receiver decodes the radio and sends the result on to us. His two stations ran an older version of the decoder, which calls the same values by different names. The altitude was there all along, under its older name. Since 16:52 UTC we understand both dialects, and a station with a decoder from another era doesn’t have to change a thing.
Two e-mails, nine wishes
The next day two e-mails came from the same man, with a list of wishes. A photo should end up on the aircraft he meant, even when another airframe’s registration begins the same way. The gallery should filter, a link from the watchlist should lead to the aircraft, a station’s records should say which aircraft set them, and the ‘took off’ and ‘landed’ alerts for one flight should not arrive together.
Each of those has its reason in the real world. Registrations get reused and many of them begin the same way, so a form that guesses the aircraft from the first few characters will sometimes guess wrong. And the two alerts came together because that flight took off where no station could hear it: we only learned about the take-off together with the landing. Two messages in the same second are worse than one true one.
By 20:54 UTC on 16 September all of it was live: the form no longer picks anything for you and shows both options when a registration is ambiguous, the gallery filters by type, airline, place and registration, a station’s records name the aircraft type, and the alert sends only the landing when the take-off would arrive late. At 21:20 he had a reply with the links.
A map that never closes
Air traffic has no closing time. When it is night in Europe, flights are taking off in Asia, and so there is no moment when nobody has the map open.
A new version of the website still often comes out several times a day. It is put together on the side, checked, and only then switched over in one go. Whoever has the map open at that moment notices nothing: the files of the previous version stay at hand, so an open tab finds its own code even after the switch. And if a new version broke something, the previous one comes back in a single step.
The chart at the top has no day at zero. The tallest bar stands on 27 September, the day the 3D airports got buildings with their real height, roofs and windows.
What it left behind
The project started on 9 August with one page of rules. One of them is still printed on the About page: what we can’t hear, we don’t claim. Seven weeks later 170 stations were sending data from people’s homes, the site spoke thirteen languages, and the archive held 7.9 billion aircraft positions and 12.2 million flights, including the imported open-data history of 2026. The rest of the numbers are in the 21 episodes before this one.
“All of this was hours, not days.” Luboš Kovář, replying to the station owner on 16 September.