SEA (Seattle) to STL (St. Louis) flights arrive on time 76% of the time. The most reliable airline on this route is Alaska Airlines at 81%. The average delay is 43 minutes. Delays on this route are most often caused by the incoming plane arriving late.
Source: Bureau of Transportation Statistics. Updated March 2026.SEA → STL
SEA (Seattle) to STL (St. Louis)
SEA → STL on-time performance by month
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JanFebMarAprMayJunJulAugSepOctNovDec
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This route is on time most of the time. About 76% of flights arrive on schedule.
Delays on this route are most often caused by the incoming plane arriving late.
Accurate?
Alaska Airlines is significantly more reliable on this route at 81% on time vs Southwest Airlines at 52%.
Airline Comparison
Alaska Airlines leads at 81% on time; Southwest Airlines trails at 52%.
Accurate?
Good to know
Departing from SEA
82% on timeExpect ~19 min sitting on the taxiway after your gate pushes back. SEA has long runway queues.
TSA is currently ~10 min. Best time: 4 AM (about 5 min).
Arriving at STL
81% on timeWhen flights into STL are late, the average delay is 63 minutes. Build buffer if you have ground plans.
If connecting at STL: TSA is ~20 min right now. Allow at least 60 minutes for a domestic connection.
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Data last updated March 2026. Source: Bureau of Transportation Statistics.