PlainFlights

Route · IAD → SEA · 2020–2025 BTS data

Washington to Seattle

According to PlainFlights' route traffic ranking (BTS On-Time Performance total flights), IAD to SEA (Washington to Seattle) ranks #1148 of 4927 tracked domestic routes by total flights (most flights = #1).

Data updated 2026-06-13

82%
On-time
+3 pts
vs US avg
73 min
Delay when late
10,097
Flights
#1148 of 4927
Corpus placement

Cancelled

1.2%

Best Month

Nov 2024 96%

Worst Month

Dec 2025 49%

Distance

2,306 mi

Carriers

9

Monthly Performance

Recent 24 months of route data.

Period Flights Delayed Cancelled Diverted Carriers
Dec 2025 124 63 1 1 DL,AS,UA
Nov 2025 119 36 3 0 UA,DL,AS
Oct 2025 156 24 2 0 AS,UA,DL
Sep 2025 179 14 0 0 UA,DL,AS
Aug 2025 221 43 1 0 UA,AS,DL
Jul 2025 245 64 2 1 AS,UA,DL
Jun 2025 240 67 3 1 AS,UA,DL
May 2025 203 33 0 0 AS,UA,DL
Apr 2025 155 23 0 0 DL,UA,AS
Mar 2025 116 20 0 0 AS,DL,UA
Feb 2025 93 33 0 1 AS,DL,UA
Jan 2025 104 22 1 0 AS,DL,UA
Dec 2024 135 22 1 1 AS,DL,UA
Nov 2024 181 8 0 1 UA,AS,DL
Oct 2024 193 15 1 0 UA,AS,DL
Sep 2024 230 27 3 0 UA,AS,DL
Aug 2024 265 53 2 2 AS,DL,UA
Jul 2024 278 52 5 0 AS,DL,UA
Jun 2024 270 93 1 2 AS,DL,UA
May 2024 226 67 0 0 AS,DL,UA
Apr 2024 146 31 0 0 AS,DL,UA
Mar 2024 118 16 0 1 AS,DL,UA
Feb 2024 95 5 0 1 AS,DL,UA
Jan 2024 105 10 23 0 AS,DL,UA

IAD–SEA seasonal on-time pattern

Best: October (90.5%) · weakest: June (72.6%)

70%75%80%85%90%95% JanFebMarAprMayJunJulAugSepOctNovDec 74.3%

Strongest calendar month

October

90.5% on-time · ~149 flights/mo

Busiest calendar month

August

~193 flights/mo avg

Weakest calendar month

June

72.6% on-time · ~173 flights/mo

Cancellation Rate

1.2%

49 of 4,197 flights

Diversion Rate

0.3%

12 of 4,197 flights

Explore origin & destination

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

IAD - Washington

Full on-time, delay-cause, and seasonal performance for Washington, DC.

IAD 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 IAD and SEA side by side on delays, cancellations, and reliability.

Compare IAD vs SEA

Origin-hub reliability standing

Mid-pack among IAD departures

From IAD, this corridor sits with 42 other 75–85% on-time routes out of 58 tracked departures, not the hub's reliability leaders (14 at ≥85%) and not the softest ( 2 below 75%). Destination: Seattle · fleet on-time rank #2350 of 4927.

What the Data Says About IAD to SEA

Bureau of Transportation Statistics records show Washington to Seattle (IAD to SEA) running a 82% on-time rate over 10,097 tracked flights, on the stronger end of a typical domestic pairing. When flights do run late, the average delay is 73.4 minutes. The 2,306-mile corridor is served by 9 carriers, and over the last 24 months 1.2% of 4,197 flights were cancelled, 0.3% diverted.

The monthly split is wide on this route: Nov 2024 posted the strongest performance at 96% on-time, while Dec 2025 came in at just 49% - a 46-point swing worth factoring into travel timing.

On the multi-year calendar, IAD–SEA peaks in October at 90.5% on-time while August carries the heaviest traffic (~193 flights per month) ; the softest month is June at 72.6%, a 17.9-point swing that repeats because the corridor's weather and holiday mix stays stable year to year.

Frequently Asked Questions

Where does IAD to SEA rank among US routes by traffic? ▼
According to PlainFlights' route traffic ranking, IAD to SEA ranks #1148 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 IAD to SEA? ▼
Flights from Washington to Seattle have a 82% on-time rate based on 10,097 flights. The average delay is 73.4 minutes. The best recent month was Nov 2024 with 96% on-time.
What is the cancellation rate for IAD to SEA? ▼
Over the last 24 months, 1.2% of flights on this route were cancelled (49 of 4,197 flights) and 0.3% were diverted.
How far is the flight from IAD to SEA? ▼
The flight distance from Washington (IAD) to Seattle (SEA) is approximately 2,306 miles. This route is served by 9 carriers.
When is the best time to fly from IAD to SEA? ▼
The best recent month for on-time performance was Nov 2024 (96% on-time). The worst was Dec 2025 (49% on-time). Consider booking during months with historically better performance.

Airports on this route

IAD Airport

Washington
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 IAD–SEA data

IAD–SEA runs 3 pts above the national 79% average; the remaining risk is month-to-month swing and carrier mix, not a weak headline rate.

  • Compare IAD and SEA airport profiles: delay causes and top routes differ even on the same corridor. IAD airport
  • If your dates flex, October (90.5% on-time) beats June (72.6%) on this corridor. Seasonal chart
  • 4 other routes post a similar 82% 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.