Alaska Airlines is the most reliable airline on the SEA to STL route with a 83% on-time rate, compared to Southwest Airlines at 59%. Based on 2,782 flights tracked.
Source: Bureau of Transportation Statistics. Updated October 2026.Best Airline: SEA to STL
Seattle to St. Louis — airline reliability comparison
On-Time Rate by Airline
Alaska Airlines83%
Southwest Airlines59%
SEA to STL Airline Comparison
| Airline | On-Time % | Cancel % | Avg Delay | Flights |
|---|---|---|---|---|
| Alaska AirlinesASBest | 83% | 0.6% | 42m | 2,782 |
| Southwest AirlinesWNWorst | 59% | 0.3% | 45m | 263 |
Route Overview
79%
Overall On-Time
43m
Avg Delay
0.4%
Cancel Rate
3,062
Total Flights
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Data last updated October 2026. Source: Bureau of Transportation Statistics.