Historical on-time performance
St. Louis to Seattle
1,709 miData through Dec 2025Source: US DOT · BTS
Flights on STL–SEA arrive on time 75% of the time over the last 12 months.
On-time rate75%arrived within 15 min
p90 delay35 min1 in 10 flights is worse (tail risk)
Cancelled0.7%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
- Alaska AirlinesbestOn-time76%Medianon timep9035 minCancel0.8%Flights774
- Southwest AirlinesOn-time55%Median5 minp9045 minCancel0.0%Flights31
Why flights run late
Delay causes
- Airline34%
- Weather8%
- Air traffic (NAS)22%
- Late aircraft36%
- Security1%
Most delay minutes here are attributed to Late aircraft.
Over time
On-time trend
By season
On-time rate by month
When to fly
Best time to fly STL → SEA
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 — 87% on time.
- Mornings87% on time · p90 15 min · 990 flights
- Afternoons79% on time · p90 25 min · 994 flights
- Middays74% on time · p90 30 min · 101 flights · limited
- Evenings68% on time · p90 45 min · 467 flights
Best day of week
On-time rates are fairly even by day on this route — ranging from 74% to 84% on time.
- Thursdays84% on time · p90 20 min · 382 flights
- Mondays83% on time · p90 25 min · 387 flights
- Wednesdays80% on time · p90 25 min · 330 flights
- Tuesdays80% on time · p90 25 min · 333 flights
- Fridays79% on time · p90 30 min · 388 flights
- Sundays78% on time · p90 30 min · 389 flights
- Saturdays74% on time · p90 35 min · 343 flights
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