Carrier route record

ASSEA→DCA

Alaska Airlines · Seattle to Washington

Flights: 729
Period: July 2025 to June 2026
Share of route: 67%
Carriers: 2

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

Alaska on SEA to DCA lands a B, about a point worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 729 flights, with a median arrival 12 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate Alaska on SEA to DCA from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

76.4%

Arrivals under 15 minutes late, of 709 completed flights

Avg delay

58 min

Across delayed arrivals only, not all flights

Cancelled

1.10%

National rate is 1.81%

Whole route

81.6%

Every carrier on SEA to DCA, 1,094 flights

These figures cover 729 flights between July 2025 and June 2026. The median arrival is 12 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.

Carrier by carrier

Alaska against every carrier on SEA to DCA

Alaska flew 729 of the 1,094 flights on SEA to DCA, most of the route. Its 76.4% on time is 5 points worse than the route as a whole, which runs 81.6%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from Delta at 92.1% to Alaska at 76.4%.

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 DCA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	365	92.1%	126 min	3.01%	A−
Alaska Airlines (this page)	729	76.4%	58 min	1.10%	B

Flight by flight

Alaska flight numbers on SEA to DCA

Departure window

When Alaska runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 23 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am—
8am–11am365 flights85.9%
11am–2pm137 flights73.0%
2pm–5pm227 flights63.3%
5pm–8pm—
8pm–5am—

Scale runs 55% to 90%. Rows with fewer than 30 flights show a dash.

Book the morning departure. Flights leaving between 8am–11am arrive on time 85.9% of the time, against 63.3% for the afternoon window. That is 23 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 365 flights scheduled in it.

Across the year

Alaska on SEA to DCA through the year

Darker means more delays. Figures are on-time percentages.April best, July worst

July is the worst month at 57.1% on time, 33 points below April, the best at 90.0%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. January was the busiest month here, with 62 flights.

Across the week, Saturday is the strongest day at 86.1% on time and Monday the weakest at 71.0%. 15 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Alaska runs late on this route

One category carries most of the weight here. National Airspace System accounts for 58% of the 9,676 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.

National Airspace System
58%
Carrier
19%
Late-arriving aircraft
12%
Extreme weather
10%

58% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 5,640 minutes out of 9,676, against a national NAS share of 21%. The split is drawn from 9,676 reported delay minutes.

Cancellations sit at 1.10% against a national 1.81%, which is ordinary. Diversions add another 1.65%.

Connections and stage length

What a delay here costs

7.6% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.

At 2,329 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 runs 76.7% on time across 729 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

One caution: this is a thin sample. 729 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 DCA

Put together: treat all of this as provisional. 729 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 76.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 709 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures