Historical on-time performance
Seattle to St. Louis
1,710 miData through Dec 2025Source: US DOT · BTS
Flights on SEA–STL arrive on time 75% of the time over the last 12 months.
On-time rate75%arrived within 15 min
p90 delay30 min1 in 10 flights is worse (tail risk)
Cancelled0.2%of scheduled flights
based on 805 flights over the last 12 months. On-time means arriving within 15 minutes (BTS standard).
By airline
How each carrier compares
Too close to call — no single carrier is clearly more on-time here.
- Southwest AirlinesOn-time58%Median5 minp9045 minCancel0.0%Flights31
- Alaska AirlinesOn-time76%Medianon timep9030 minCancel0.3%Flights774
Why flights run late
Delay causes
- Airline39%
- Weather0%
- Air traffic (NAS)21%
- Late aircraft39%
- Security0%
Most delay minutes here are attributed to Airline.
Over time
On-time trend
By season
On-time rate by month
When to fly
Best time to fly SEA → STL
All airlines · rolling 36 months (2023-01 .. 2025-12).
Best time of day
Mornings are the most reliable time of day to fly this route — 83% on time.
- Mornings83% on time · p90 20 min · 1,019 flights
- Evenings75% on time · p90 35 min · 870 flights
- Middays66% on time · p90 40 min · 641 flights
Best day of week
On-time rates are fairly even by day on this route — ranging from 73% to 77% on time.
- Saturdays77% on time · p90 35 min · 337 flights
- Mondays77% on time · p90 30 min · 387 flights
- Sundays76% on time · p90 30 min · 390 flights
- Wednesdays76% on time · p90 35 min · 330 flights
- Tuesdays76% on time · p90 30 min · 331 flights
- Fridays74% on time · p90 40 min · 391 flights
- Thursdays73% on time · p90 30 min · 387 flights
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