Edmonton (YEG) Traffic Down 62% on Sunday 1 November 2026 — a Day of Freezing Fog, Not a Gap in Our Data

What fired, and what we checked. Our detection layer flagged YEG when Sunday 1 November came in at 93 observed movements against a rolling seven-day average of ~256 — a −64% traffic anomaly at the airport. Against the four Sundays before it (~243 a day) the reading is −62%. A drop that size can be an operational event or a failure of the instrument, so automated multi-signal analysis checks it against every other layer we track before anything is claimed: the hour-by-hour shape of the count, the flights behind it, a second receiver network, neighbouring airports, weather, closure signals and GNSS interference. Here, unlike the Alicante coverage anomaly in October, the layers line up on a real thinning of traffic — and on one candidate cause.

A day of freezing fog. Edmonton's routine weather reports were VFR through the evening of 31 October local time. At 08:04 UTC on 1 November they turned to freezing fog — visibility half a mile, vertical visibility 200 ft — and then worsened: 1/8 mile for much of the day, a report of zero visibility with fog estimated at about 300 ft at 17:00 UTC, runway visual range on runway 02 mostly between 700 and 2,600 ft. In all, 32 of 33 reports from 08:04 UTC on 1 November to 07:00 UTC on 2 November put visibility at or below half a mile; 25 of the 38 reports on 1 November were LIFR, against 17 in the 791 reports of 3–31 October. Winds stayed near calm, which is what lets radiation fog sit. Saskatoon, 480 km east, logged LIFR in 28 of its 39 reports the same day; Calgary, 246 km south, logged 24 VFR reports with visibility of at least 12 miles. As interpretation rather than measurement: in visibility this low, whether an arrival can land depends on the runway's approach equipment and on each aircraft's and crew's low-visibility approval, and departures thin out later in the day when the aircraft that would fly them did not arrive. That fits the shape we measured — a morning bank of 32 departures against 47, then 4 departures and 6 arrivals after 17:00 UTC against 47 and 59.

The flights did not fly from here — they did not vanish from our view. The test that separates a real drop from lost coverage is continuity. We took every callsign that departed Edmonton in our records on 11–31 October and counted their flights on each day, from any airport. On 1 November they flew 221 times, against 303 on 25 October; 54 departed Edmonton (129 the Sunday before), 122 departed somewhere else (134), and 45 could not be tied to any departure airport (40). The untagged share did not move — the signature of a receiver outage, as at Alicante, is that it jumps. The inbound side shows where some flights went: callsigns that had landed at Edmonton earlier in the month flew 229 times on 1 November against 303, landed at Edmonton 31 times against 98 — and landed at Calgary 39 times, against 7 on 25 October. We label the method honestly: a callsign is a flight number, not a specific aircraft or rotation, and this is a continuity indicator, not a diversion log. It is consistent with flights diverting to Calgary or not operating, and not consistent with flights operating normally out of our sight.

A second network saw it too; Calgary did not. We cross-check against a second crowdsourced ADS-B aggregate built on different volunteer receivers. It recorded 119 movements at Edmonton on 1 November (68 departures, 51 arrivals), against 234 and 252 on the two Sundays before — −51% — and 445 at Calgary, exactly its count of 25 October. In our own feed Calgary read 415 against 430. Our feed was softer network-wide on 1 November — 13% below 25 October at the same point of ingestion, with Vancouver and Toronto down by about that much — but that is a fraction of Edmonton's fall, and the second network does not share it at Calgary. Saskatoon, also in fog, recorded 30 departures in our feed against 39 on 25 October; at a smaller airport that difference is within normal noise, and we do not read it as an event.

No closure, no interference — and one blind spot. No closure event registered in the Edmonton FIR (CZEG) in our records this autumn — a FIR-level statement about airspace signals, not a claim about operations at Edmonton, which belong to the airport, the airlines and Canadian aviation authorities. Next door, the Winnipeg FIR (CZWG) carries a low-confidence (0.18) flag of unknown cause spanning 29 October to 1 November, built on two weak signals; nothing in the movement counts corroborates it, and we do not link it to Edmonton. GNSS interference across CZEG sat at 0.03% of aircraft on 1 November (5 of 18,381), in line with 0–0.07% on 26–31 October, and the airport's own seven-day interference ratio is zero. The blind spot we name: our NOTAM set carries no records for the Edmonton FIR at all, so we cannot say whether a notice was issued for YEG on 1 November.

What would change this page. Three things decide it. The settling count: 1 November settles on the nightly refresh of 5 November; we expect a few more movements, not ~150. The next day: visibility at Edmonton was back to VFR by 08:51 UTC on 2 November; if Monday 2 November reads near the ~300 movements of recent Mondays (280, 301 and 320 on 12, 19 and 26 October), this closes as a one-day weather event; if traffic stays low with the weather clear, the page stays open and the fog reading weakens. An official signal: a closure, a NOTAM or an operational notice for YEG appearing in any layer would sharpen or change the framing. Until then we publish measured signals and their timing, not conclusions about why individual flights did not operate.