SEA to STL flight delays & on-time performance
Nonstop flights from Seattle–Tacoma International Airport to St. Louis Lambert International Airport · 1,709 miles · Aug 2025 – Jul 2026
No FAA-reported ground stops or delays at SEA or STL right now. Individual flights can still be delayed by the airline; check with your airline for your flight.
Key facts
- Flights from Seattle (SEA) to St. Louis (STL) arrived on time 83% of the time in Aug 2025 – Jul 2026, better than the 78% national average.
- 0.3% were cancelled, and 3% arrived an hour or more late.
- Alaska Airlines was the most punctual airline here (84% on time); Southwest Airlines was the least (73%).
- Departures scheduled around 7am did best (96% on time); around 11am did worst (65%).
- Tuesday was the most reliable day to fly (91% on time) and Saturday the least (77%).
- The largest source of delay minutes was late-arriving aircraft (41%).
Which airline is most on time from SEA to STL?
Ranked by on-time arrival rate. Regional airlines fly under their partner's brand (e.g. SkyWest for Delta Connection or United Express).
| Airline | On time | Cancelled | Avg delay | 1 hr+ late | Flights |
|---|---|---|---|---|---|
| Alaska Airlines | 84% | 0.3% | 8 min | 2.8% | 780 |
| Southwest Airlines | 73% | 1.0% | 14 min | 3.9% | 103 |
Best time of day to fly
On-time arrival rate by scheduled departure hour (local time).
- 7am96%112 flights
- 8am86%97 flights
- 9am89%175 flights
- 10am65%20 flights
- 11am65%71 flights
- 12pm65%78 flights
- 1pm88%52 flights
- 5pm91%57 flights
- 6pm81%221 flights
Best day of the week
On-time arrival rate by day of departure.
- Monday80%0.0% cancelled
- Tuesday91%0.9% cancelled
- Wednesday88%0.0% cancelled
- Thursday79%0.0% cancelled
- Friday85%0.7% cancelled
- Saturday77%0.0% cancelled
- Sunday84%0.7% cancelled
On-time trend by month
Why flights are late
Share of delay minutes by cause, as reported by airlines to the DOT.
- Late-arriving aircraft41%
- Airline (crew, maintenance, cleaning, fueling)40%
- Air traffic control & airport congestion16%
- Extreme weather3%
- Security0%
Why flights are cancelled
Share of cancellations by reason.
- Extreme weather100%
- Airline (crew, maintenance, cleaning, fueling)0%
- Air traffic control & airport congestion0%
- Security0%
SEA to STL: common questions
- How often are SEA to STL flights on time?
- 83% of flights arrived less than 15 minutes late in Aug 2025 – Jul 2026, compared with 78% for all US flights.
- How often are flights from Seattle to St. Louis cancelled?
- 0.3% of scheduled flights were cancelled (3 of 883).
- How long are typical delays?
- Across all flights the average arrival delay was 9 min (early arrivals count as zero). Flights that were late arrived 46 min behind schedule on average, and 3.0% of flights were an hour or more late.
- How long is taxi time at SEA?
- Flights on this route spent 23 min taxiing from the gate to takeoff on average.
Related routes
Return trip: STL to SEA — 79% on time
More flights from Seattle
Data: U.S. DOT Bureau of Transportation Statistics, Aug 2025 – Jul 2026 (12 months). Latest month published by BTS: July 2026. Route: SEA → STL, nonstop flights by US airlines that report to the DOT. How we calculate this.