The tails we will not track
Somebody tried to put a Comco Ikarus C42 into their hangar this morning. They typed its registration, D-MXFG, into the box that asks for an aircraft address, and the page answered that the code had to be six characters long. D-MXFG is six characters long. That is the kind of error message that makes you doubt the whole site.
Two different things were wrong, and only one of them was the message.
What the box actually wanted
Aircraft carry two names. One is the registration painted on the tail, the one people know. The other is a 24-bit address the transponder broadcasts, written as six hexadecimal characters, which trackers usually label "Mode S". The hangar wants the second, because it is the only name our receivers ever hear.
The field now says which one it wants, and when you hand it a tail number it says so plainly instead of counting your characters. Pasting the address with a bit of text around it no longer gets silently cut off either.
Why we could not find it anyway
The search above that box looks through the aircraft our own receivers are hearing at this moment. There is no registration database behind it. If a tail is not in the air over one of our antennas, we do not know its name, and no amount of typing changes that.
For this aircraft there is a second reason, and it is the one worth writing down. Light aircraft, microlights, gliders and balloons are anonymised everywhere on Skydex. They appear on the map as unnamed blips with a position, an altitude and a class, and nothing else. No address, no registration, no callsign. Somebody's two-seater is not a fleet movement, it is a person's afternoon, and we have taken that line since the day the aircraft layer opened.
The search was telling those people the wrong thing. "Nothing matches right now" reads as "try again later", and for this whole class of aircraft the honest answer is "never". It says that now.
The part nobody could see
Here is the real bug. The search could not offer a private tail, so we had assumed none could reach a hangar. But the address box accepts anything six characters long, and every public tracker prints the address for free. Type it in and the aircraft went straight into the hangar, where the page would cheerfully tell you which days our receivers had heard it and which stations picked it up.
That is a movement log for an identifiable person's aircraft. We do not publish one even for military airframes, which broadcast deliberately and which our own rules say get no history and no alerts, ever. A microlight was getting more than a transport jet.
So the network now writes down its verdict while the aircraft is overhead, which is the only moment it can be taken: once it lands there is nothing left to read. The hangar checks that verdict before it accepts a tail, before it shows a history, before it offers an alert. Where the verdict has not been recorded yet, the aircraft type covers a good part of the gap on its own, and the rest closes the next time the aircraft flies past one of us.
If you already had such a tail starred, the history and the bell are gone. The list entry stays. Nothing else about your hangar changes.