STL to SEA flight delays & on-time performance
Nonstop flights from St. Louis Lambert International Airport to Seattle–Tacoma International Airport · 1,709 miles · Aug 2025 – Jul 2026
No FAA-reported ground stops or delays at STL or SEA right now. Individual flights can still be delayed by the airline; check with your airline for your flight.
Key facts
- Flights from St. Louis (STL) to Seattle (SEA) arrived on time 79% of the time in Aug 2025 – Jul 2026, better than the 78% national average.
- 0.9% were cancelled, and 4% arrived an hour or more late.
- Alaska Airlines was the most punctual airline here (82% on time); Southwest Airlines was the least (53%).
- Departures scheduled around 6am did best (95% on time); around 11am did worst (42%).
- Wednesday was the most reliable day to fly (86% on time) and Saturday the least (67%).
- The largest source of delay minutes was late-arriving aircraft (36%).
Which airline is most on time from STL to SEA?
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 | 82% | 1.0% | 10 min | 3.4% | 781 |
| Southwest Airlines | 53% | 0.0% | 20 min | 5.8% | 103 |
Best time of day to fly
On-time arrival rate by scheduled departure hour (local time).
- 6am95%166 flights
- 7am86%156 flights
- 11am42%33 flights
- 12pm59%32 flights
- 2pm87%128 flights
- 3pm72%111 flights
- 4pm83%96 flights
- 5pm48%23 flights
- 6pm71%31 flights
- 7pm69%98 flights
Best day of the week
On-time arrival rate by day of departure.
- Monday80%2.2% cancelled
- Tuesday85%0.0% cancelled
- Wednesday86%0.0% cancelled
- Thursday73%0.7% cancelled
- Friday79%0.7% cancelled
- Saturday67%1.7% 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 aircraft36%
- Air traffic control & airport congestion30%
- Airline (crew, maintenance, cleaning, fueling)29%
- Extreme weather4%
- Security1%
Why flights are cancelled
Share of cancellations by reason.
- Extreme weather75%
- Airline (crew, maintenance, cleaning, fueling)25%
- Air traffic control & airport congestion0%
- Security0%
STL to SEA: common questions
- How often are STL to SEA flights on time?
- 79% 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 St. Louis to Seattle cancelled?
- 0.9% of scheduled flights were cancelled (8 of 884).
- How long are typical delays?
- Across all flights the average arrival delay was 11 min (early arrivals count as zero). Flights that were late arrived 48 min behind schedule on average, and 3.7% of flights were an hour or more late.
- How long is taxi time at STL?
- Flights on this route spent 15 min taxiing from the gate to takeoff on average.
Related routes
Return trip: SEA to STL — 83% on time
More flights from St. Louis
Data: U.S. DOT Bureau of Transportation Statistics, Aug 2025 – Jul 2026 (12 months). Latest month published by BTS: July 2026. Route: STL → SEA, nonstop flights by US airlines that report to the DOT. How we calculate this.