STL to SEA flight delays
St. Louis, MO (STL) Seattle, WA (SEA) · 1,709 miles
118 flights · March 2025 – August 2026 · US Bureau of Transportation Statistics
71.19%
Arrived on time
Within 15 minutes of schedule
0%
Cancelled
Share of scheduled flights
49 min
When late, late by
Average across delayed arrivals
15 min
Delay per flight
Averaged over every flight flown
What the record says about this route
The two directions do not behave alike. SEA to STL arrives on time 17.7 points more often than the outbound. Delay accumulates through the flying day, so whichever direction is scheduled later tends to carry the worse record — which is an argument for booking the morning departure if the choice exists.
Flights from St. Louis to Seattle run late more often than the average route, though not severely.
Every airline on STL to SEA
Ranked by how many flights each one operated. A carrier with fewer than 100 flights in the period is listed but not graded.
| Airline | Flights | On time | Cancelled | Avg delay | Grade |
|---|---|---|---|---|---|
| Alaska Airlines | 90 | 82.22% | 0% | 49 min | — |
| Southwest Airlines | 28 | 35.71% | 0% | 48 min | — |
The return leg
SEA to STL Seattle back to St. Louis 88.89% on time AOther routes from St. Louis
Common questions
Are flights from St. Louis to Seattle usually delayed?
71.19% of flights on the STL to SEA route arrived within 15 minutes of schedule, so roughly 3 in every ten arrived late. That is worse than the average route in this record.
How often are STL to SEA flights cancelled?
0% of scheduled flights did not operate — about 1 in every thousand. That is in the normal range.
When STL to SEA flights are late, how late are they?
About 49 minutes on average across the flights that arrived more than 15 minutes behind schedule.
What these figures do and do not tell you
Everything on this page is counted from the flights that actually operated on STL to SEA during March 2025 – August 2026, as reported by the airlines to the US Bureau of Transportation Statistics. "On time" is the federal definition: arriving at the gate within 15 minutes of the scheduled time.
A route's record is a description of the past, not a forecast. Weather, air traffic control and the aircraft's earlier flights that day drive most delays, and none of them are predictable from a historical rate. What the record does tell you is whether this route runs late more often than others, and which carrier on it has the better history — which is the part you can actually act on when you book.
Cancellations are counted separately from delays because they are a different problem for a traveller: a late flight still gets you there. How the grade is calculated →