Carrier route record

ASSEA→IAD

Alaska Airlines · Seattle to Washington

Flights: 835
Period: September 2025 to August 2026
Share of route: 46%
Carriers: 3

Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Alaska Airlines.

Alaska on SEA to IAD lands a B+, 6 points better than the national rate of 77.3%. About one flight in six arrives 15 minutes late or worse, and those flights are late by roughly 40 minutes on average. That rests on 835 flights, with a median arrival 8 minutes early.

Set against the rest of the country, Alaska's SEA to IAD record is 6 points better than the US average of 77.3%. That gap is worth roughly 60 fewer late arrivals for every thousand flights.

On time

83.3%

Arrivals under 15 minutes late, of 828 completed flights

Avg delay

38 min

Across delayed arrivals only, not all flights

Cancelled

0.36%

National rate is 1.89%

Whole route

84.8%

Every carrier on SEA to IAD, 1,822 flights

These figures cover 835 flights between September 2025 and August 2026. The median arrival is 8 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

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Carrier by carrier

Alaska against every carrier on SEA to IAD

Alaska flew 835 of the 1,822 flights on SEA to IAD, about 46% of it. Its 83.3% on time is 2 points worse than the route as a whole, which runs 84.8%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from United at 91.4% to Delta at 76.7%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on SEA to IAD
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	626	91.4%	76 min	0.64%	A+
Alaska Airlines (this page)	835	83.3%	38 min	0.36%	B+
Delta Air Linesthin sample	361	76.7%	80 min	1.11%	B

Flight by flight

Alaska flight numbers on SEA to IAD

AS 36722:4383.0% · 284 flights

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Departure window

When Alaska runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 835 flights.

5am–8am—
8am–11am365 flights83.6%
11am–2pm—
2pm–5pm186 flights83.2%
5pm–8pm—
8pm–5am284 flights83.0%

Scale runs 75% to 90%. Rows with fewer than 30 flights show a dash.

The overnight block holds up unusually well at 83.0% on time across 284 flights. Red-eyes fly into empty airspace and empty gates, and they are the first rotation of the aircraft's day rather than the last. The 8am–11am window is the busiest, with 365 flights scheduled in it.

Across the year

Alaska on SEA to IAD through the year

Darker means more delays. Figures are on-time percentages.December best, January worst

January is the weak month at 74.3% on time, against 92.2% in December. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. August was the busiest month here, with 93 flights.

Across the week, Wednesday is the strongest day at 92.0% on time and Monday the weakest at 78.1%, a spread of 14 points.

Arrival by arrival

How late Alaska on SEA to IAD runs when it is late

Alaska on SEA to IAD often beats the schedule: 276 of 828 completed flights, 33%, arrived 15 minutes or more early. Most of the lateness is short. 69 of the 138 late arrivals were under half an hour behind, and 16 reached an hour or more.

15+ min early276 flights33.3%
Within 15 min414 flights50.0%
15–29 min late69 flights8.3%
30–59 min late53 flights6.4%
1–2 hours late12 flights1.4%
2+ hours late4 flights0.5%

Scale runs 0% to 100%.

Share of 828 completed flights by arrival against schedule.

A late pushback is often recovered here: of 194 departures that left 15 minutes late or more, 83 still arrived on time. 27 flights left on time and still arrived late.

The worst days

Worst days for Alaska on SEA to IAD

The latest arrival of the period was on 13 March 2026, 2 hours 36 minutes behind schedule; most of its delay minutes were filed as extreme weather. On three of the five worst days the largest share was filed as carrier-caused (crew, maintenance, fuelling, baggage).

The latest arrivals of Alaska on SEA to IAD in the period
Date	Arrived late by	Largest filed cause
13 March 2026	2 hours 36 minutes	Extreme weather
24 August 2026	2 hours 12 minutes	National Airspace System
4 November 2025	2 hours 6 minutes	Carrier
3 April 2026	2 hours 2 minutes	Carrier
23 October 2025	1 hour 52 minutes	Carrier

Delay causes

Why Alaska runs late on this route

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 5,179 reported delay minutes.

Carrier
40%
Late-arriving aircraft
36%
National Airspace System
19%
Extreme weather
4%
Security
0%

36% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 5,179 reported delay minutes here, that single category outweighs weather by 10 to one. The split is drawn from 5,179 reported delay minutes.

The largest share of delay minutes, 40%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,097 of the 5,179 delay minutes reported here.

Cancellations are rare at 0.36%, below the national 1.89% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 1.9% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

At 2,305 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.

The return leg is a different operation and performs like one: it runs 75.4% on time across 835 flights, 8 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 8 points of difference.

One caution: this is a thin sample. 835 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking Alaska on SEA to IAD

Put together: treat all of this as provisional. 835 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 83.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 828 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures