Seattle-Tacoma International Airport (SEA) logs an average arrival delay rate of 21.4% and an average departure delay rate of 18.7% across the seven-day Thanksgiving travel window. Fourteen days out from peak volume, SEA is FlightCheck’s most-monitored facility, with 19 active user trackers.
Capacity & Airfield Constraints
SEA operates three parallel runways (16L/34R, 16C/34C, 16R/34L), but close lateral spacing restricts parallel instrument approaches. Separation between 16L and 16C is just 800 feet, precluding simultaneous independent operations in Instrument Meteorological Conditions (IMC).
Under Visual Meteorological Conditions (VMC), SEA maintains an Airport Acceptance Rate (AAR) of 48–52 arrivals per hour. In IMC, the FAA drops the AAR to 32–36 arrivals per hour. Because 16R/34L absorbs nearly all widebody and long-haul arrival streams due to length and noise abatement, SEA functions essentially as a single-runway arrival dependency during bad weather.
November Meteorological Hazards
Late-November operations at SEA face three recurring weather drivers:
* Radiation & Valley Fog: Forms overnight in the Duwamish and Green River valleys. Ceilings frequently fall below Cat I minimums (200 ft / RVR 2,400) between 05:30 and 09:30 PST.
* Puget Sound Convergence Zones (PSCZ): Generates localized bands of moderate-to-heavy rain, sudden visibility drops, and wind shifts over the runway complex.
* Sustained South-Southwest Winds: Ocean systems funneling through the Puget Sound basin produce persistent gusts of 25–35 knots, creating severe low-level wind shear (LLWS) and challenging crosswind components on the 16/34 alignment.
Diurnal Delay Pattern
Delays follow a predictable operational curve:
* 06:00–10:00 PST: Peak ground stop and Ground Delay Program (GDP) window. Fog suppresses arrival rates. Inbound aircraft hold in eastern Washington and northern Oregon airspace. Fog burns off via solar insolation between 09:45 and 10:15 PST.
* 10:00–13:30 PST: Recovery window. Air traffic control increases metering rates to clear morning backlogs.
* 14:00–20:00 PST: Secondary delay wave. Frontal rain and gusty surface winds coincide with peak scheduled passenger volume. Cascading gate holds and taxiway congestion expand average turn times by 16 minutes.
Hub Vulnerability: Alaska Airlines
Alaska Airlines controls over 50% of SEA gate movements, running scheduled domestic turn windows as tight as 40 to 45 minutes.
During Thanksgiving operational loads (>92% load factors), this margin disappears:
* Inbound taxi delays average 12–18 minutes during afternoon pushes.
* Inter-terminal transfers—particularly between Concourse N (North Satellite) and Concourses A or B via the Satellite Transit System (STS)—require 20–25 minutes curb-to-curb under heavy foot traffic.
* Connections under 50 minutes scheduled after 13:00 PST carry a historical holiday misconnect rate of 34%. Safe hub transit requires a minimum connection buffer of 70 minutes.