Route reliability record
DCA→SEA
Washington to Seattle
- Flights
- 1,092
- Period
- September 2025 to August 2026
- Distance
- 2,329 mi
- Carriers
- 2
This route sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 1,092 DCA to SEA flights, with a median arrival 5 minutes early.
Best time to fly DCA to SEA: a 8am–11am departure, ideally on a Saturday. Flights in that window arrived on time 79.9% of the time and Saturday flights 85.5%, against 73.4% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
73.4%
Arrivals under 15 minutes late, of 1,071 completed flights
Avg delay
66 min
Across delayed arrivals only, not all flights
Cancelled
1.37%
National rate is 1.89%
Best carrier
Alaska
76.4% on time across 728 flights
These figures cover 1,092 flights between September 2025 and August 2026. Beyond the headline rate, 8.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on DCA to SEA
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.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Alaska Airlines | 728 | 76.4% | 50 min | 0.69% | B+ |
| Delta Air Linesthin sample | 364 | 67.2% | 88 min | 2.75% | C |
Flight by flight
Flights on DCA to SEA
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Washington to Seattle
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 3 of the top 4 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. IAD → SEAWashington to Seattle | United Airlines | 80.9% | 81.3% | 0.48% | 8am–11am, Sat | UA 326 17:55 |
| 2. DCA → SEAWashington to Seattle | Alaska Airlines | 75.9% | 76.4% | 0.69% | 8am–11am, Sat | AS 1 08:00 |
| 3. IAD → SEAWashington to Seattle | Alaska Airlines | 74.5% | 75.4% | 1.20% | 8am–11am, Thu | — |
| 4. BWI → SEABaltimore to Seattle | Alaska Airlines | 67.6% | 68.2% | 0.83% | 8am–11am, Mon | AS 379 18:07 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
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 1,092 flights.
- 5am–8am—
- 8am–11am365 flights79.9%
- 11am–2pm—
- 2pm–5pm238 flights70.0%
- 5pm–8pm489 flights70.1%
- 8pm–5am—
Scale runs 60% to 85%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 79.9% of the time, against 70.0% for the afternoon window. That is 10 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 489 flights scheduled in it.
Explore
Filter DCA to SEA by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On DCA to SEA, the best departure window is 8am–11am at 79.9% on time and the worst is 2pm–5pm at 70.0%, a real gap of 9.9 points. All US flights leaving 8am–11am ran 83.9%.
- 5–8am—
- 8–11am79.9%
- 11am–2pm—
- 2–5pm70.0%
- 5–8pm70.1%
- 8pm–5am—
best all US flightsScale 60% to 95%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 40 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
December is the weak month at 45.1% on time, against 85.6% in April. 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. January was the busiest month here, with 93 flights.
Across the week, Saturday is the strongest day at 85.5% on time and Wednesday the weakest at 67.9%, a spread of 18 points.
Delay causes
Why this route gets delayed
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 19,000 reported delay minutes.
- 39%National Airspace System
- 26%Late-arriving aircraft
- 26%Carrier
- 9%Extreme weather
39% 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 7,352 minutes out of 19,000, against a national NAS share of 21%. The split is drawn from 18,697 reported delay minutes.
Cancellations sit at 1.37% against a national 1.89%, which is ordinary. Diversions add another 0.55%.
Connections and stage length
What a delay here actually costs
8.6% of arrivals land an hour or more late, close to the national 8.3%, so 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 is a different operation and performs like one: it runs 82.6% on time across 1,092 flights, 9 points above 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 9 points of difference.
One caution: this is a thin sample. 1,092 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.
Work out the risk of missing a connection in SEA after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 1,092 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 73.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,071 completed flights over 12 months sit behind that.
Common questions
DCA to SEA questions
How often is DCA to SEA delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 26.6% of the 1,092 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
How reliable is DCA to SEA compared with the rest of the country?
73.4% of flights arrive on time here against a national 77.3%, a difference of 4 points against it. That is worth a C on this site's grading scale.
What time of day has the fewest delays on DCA to SEA?
The 8am–11am departure window is the strongest at 79.9% on time. The 2pm–5pm window is the weakest at 70.0%, 10 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are December delays on DCA to SEA?
December is the weakest month at 45.1% on time, compared with 85.6% in April. Across the year that is 40 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SEA to DCA — the return legseparate record
- Ronald Reagan Washington National (DCA) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Alaska Airlines on DCA to SEA76.4%
- Delta Air Lines on DCA to SEA67.2%
- DCA to BOS, a related route70.1%
- LAX to SEA, a related route85.0%
- DCA to ORD, a related route73.8%
- Alaska Airlines on-time record76.4%
- Delta Air Lines on-time record67.2%
- The best time of day to fly, according to 7.05 million flight records
- Connecting flights: how much buffer the data says you need
Direction matters. DCA to SEA and SEA to DCA are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.