PlainFlights

Route · STL → SEA · 2020–2025 BTS data

St. Louis to Seattle

According to PlainFlights' route traffic ranking (BTS On-Time Performance total flights), STL to SEA (St. Louis to Seattle) ranks #2797 of 4927 tracked domestic routes by total flights (most flights = #1).

Data updated 2026-06-13

82.1%
On-time
+3.1 pts
vs US avg
57 min
Delay when late
4,262
Flights
#2797 of 4927
Corpus placement

Cancelled

0.9%

Best Month

Oct 2024 97%

Worst Month

Dec 2025 56%

Distance

1,709 mi

Carriers

3

Monthly Performance

Recent 24 months of route data.

Period Flights Delayed Cancelled Diverted Carriers
Dec 2025 54 24 1 0 AS
Nov 2025 50 4 1 0 AS
Oct 2025 61 7 0 1 AS
Sep 2025 98 17 0 0 WN,AS
Aug 2025 111 35 0 1 WN,AS
Jul 2025 123 40 1 0 AS,WN
Jun 2025 116 43 1 0 AS,WN
May 2025 79 17 1 0 AS
Apr 2025 59 7 0 0 AS
Mar 2025 52 8 0 0 AS
Feb 2025 38 7 0 0 AS
Jan 2025 34 7 1 0 AS
Dec 2024 54 8 0 0 AS
Nov 2024 50 5 0 0 AS
Oct 2024 60 2 0 0 AS
Sep 2024 100 13 0 0 WN,AS
Aug 2024 110 27 0 0 AS,WN
Jul 2024 122 24 2 0 AS,WN
Jun 2024 117 31 0 0 AS,WN
May 2024 78 27 0 0 AS
Apr 2024 60 9 1 0 AS
Mar 2024 56 4 1 0 AS
Feb 2024 37 4 0 0 AS
Jan 2024 38 3 5 1 AS

STL–SEA seasonal on-time pattern

Best: November (89.0%) · weakest: December (74.5%)

70%75%80%85%90% JanFebMarAprMayJunJulAugSepOctNovDec 74.5%

Strongest calendar month

November

89.0% on-time · ~44 flights/mo

Busiest calendar month

July

~93 flights/mo avg

Weakest calendar month

December

74.5% on-time · ~45 flights/mo

Cancellation Rate

0.9%

15 of 1,757 flights

Diversion Rate

0.2%

3 of 1,757 flights

Explore origin & destination

On-time and delay data for the airports this route connects.

STL - St. Louis

Full on-time, delay-cause, and seasonal performance for St. Louis, MO.

STL on-time profile

SEA - Seattle

Full on-time, delay-cause, and seasonal performance for Seattle, WA.

SEA on-time profile

Compare the two airports

See STL and SEA side by side on delays, cancellations, and reliability.

Compare STL vs SEA

Origin-hub reliability standing

Mid-pack among STL departures

From STL, this corridor sits with 45 other 75–85% on-time routes out of 51 tracked departures, not the hub's reliability leaders (5 at ≥85%) and not the softest ( 1 below 75%). Destination: Seattle · fleet on-time rank #2330 of 4927.

What the Data Says About STL to SEA

Bureau of Transportation Statistics records show St. Louis to Seattle (STL to SEA) running a 82.1% on-time rate over 4,262 tracked flights, on the stronger end of a typical domestic pairing. When flights do run late, the average delay is 57.0 minutes. The 1,709-mile corridor is served by 3 carriers, and over the last 24 months 0.9% of 1,757 flights were cancelled, 0.2% diverted.

The monthly split is wide on this route: Oct 2024 posted the strongest performance at 97% on-time, while Dec 2025 came in at just 56% - a 41-point swing worth factoring into travel timing.

On the multi-year calendar, STL–SEA peaks in November at 89.0% on-time while July carries the heaviest traffic (~93 flights per month) ; the softest month is December at 74.5%, a 14.5-point swing that repeats because the corridor's weather and holiday mix stays stable year to year.

Frequently Asked Questions

Where does STL to SEA rank among US routes by traffic? ▼
According to PlainFlights' route traffic ranking, STL to SEA ranks #2797 of 4927 tracked domestic routes by total flights (most flights = #1). That ordinal matches our busiest-routes listing (total_flights DESC). See /methodology#corpus-placement for the exact sort basis.
How often are flights delayed from STL to SEA? ▼
Flights from St. Louis to Seattle have a 82.1% on-time rate based on 4,262 flights. The average delay is 57.0 minutes. The best recent month was Oct 2024 with 97% on-time.
What is the cancellation rate for STL to SEA? ▼
Over the last 24 months, 0.9% of flights on this route were cancelled (15 of 1,757 flights) and 0.2% were diverted.
How far is the flight from STL to SEA? ▼
The flight distance from St. Louis (STL) to Seattle (SEA) is approximately 1,709 miles. This route is served by 3 carriers.
When is the best time to fly from STL to SEA? ▼
The best recent month for on-time performance was Oct 2024 (97% on-time). The worst was Dec 2025 (56% on-time). Consider booking during months with historically better performance.

Airports on this route

STL Airport

St. Louis
SEA Airport

Seattle
Data source

Data Source: Bureau of Transportation Statistics (BTS), On-Time Performance Data. Statistics reflect cumulative performance across all available reporting periods.

Read our methodology - how this data is sourced, computed, and verified.

Using STL–SEA data

STL–SEA runs 3.1 pts above the national 79% average; the remaining risk is month-to-month swing and carrier mix, not a weak headline rate.

  • Compare STL and SEA airport profiles: delay causes and top routes differ even on the same corridor. STL airport
  • If your dates flex, November (89.0% on-time) beats December (74.5%) on this corridor. Seasonal chart
  • 4 other routes post a similar 82.1% on-time rate; compare before you commit to this pairing. Similar routes

On-time rate reflects the BTS historical average across all reporting carriers on this origin–destination pair, not any single flight or booking recommendation.

Data sourced from U.S. Department of Transportation Bureau of Transportation Statistics (BTS) On-Time Performance data. See our methodology for details. Retrieved and formatted by PlainFlights

Every figure on PlainFlights is rendered directly from BTS On-Time Performance data, no number is typed in by an editor. This page aggregates this specific route's on-time performance and monthly trend, live from the dataset. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.