Airline-dle
On most days there is no clue at all, and on the rest it is the radio callsign
Airline-dle asks you to name one carrier in six guesses, from a pool of 682, of which 680 take a turn as the answer. On the days it can be shown, the clue is the airline's radio callsign: the word said on the frequency, which is frequently nothing like the name painted on the tail.
The callsign clue, and the days it stays away
British Airways answers to SPEEDBIRD, Pan Am was CLIPPER, South African is SPRINGBOK. The hint starts fully masked, one dot per letter, with spaces and hyphens left visible so you can see the length and the word shape. Each wrong guess uncovers one more letter, first the opening letter, then the closing one, then the rest front to back.
There is a catch, and it is the interesting part. Plenty of callsigns are simply the airline's name said out loud, so showing one would hand over the answer. The build tests every callsign against the carrier's name and aliases and marks only the ones that cannot leak it. On the days where the callsign would give the answer away, no callsign panel is rendered at all, rather than a broken or useless one, and the columns are the whole clue.
What the five columns tell you
Country, Region, Status and Alliance are match-or-miss, and Founded is a decade with an arrow pointing toward the answer. Region is a coarse but reliable first cut; country is a much harder hit.
Status is the column that gives this game its character. The pool holds active and defunct carriers side by side, so a green Status cell tells you a great deal about which half of the field you are in. Alliance is similarly lopsided, because most carriers belong to no alliance at all.
Where the data comes from
Two sources: OpenFlights, under the Open Database License (ODbL) 1.0, and Wikidata, CC0 1.0, for region, founding decade, alliance, hub and headquarters. The build first keeps only carriers that have an IATA code, a callsign and a country, which leaves a list of 1,136, then cuts that down to the 682 with enough Wikipedia coverage to count as recognisable. The calendar runs one carrier a day for 680 days.
The reveal gives the name, the codes, the full callsign where one was hidden, and, for about four carriers in five, an English Wikipedia summary excerpt under CC BY-SA 4.0. For a defunct carrier it also shows the year it ceased operations, where Wikidata records one.
After the puzzle
Finishing opens a short questionnaire built from facts that never appear in the guess grid: which of two carriers was founded earlier, which of these is now defunct, which one belongs to a named alliance, which one is based in a named region or comes from a named country, which one is based at a named hub airport, and which one is headquartered in a named city.
Hub and headquarters are only attached where the underlying record could be matched to one carrier without ambiguity, which is why some carriers carry them and some do not. The home-country round is the one that appears on some days and not others.
Questions
Is it the same puzzle for everyone?
Yes. One carrier a day, the same for every player, rolling over at midnight UTC. The bonus questions are seeded from the puzzle number, so those are shared too.
Do I need an account?
No. There is no sign-up. Streaks and stats are kept in your browser's local storage rather than on a server.
Why is there no callsign clue today?
Because today's callsign would give the answer away. Only the carriers whose callsign cannot leak the name get a hint panel, so on most days it is withheld entirely and you play on the columns alone.