Route reliability record
DCA→SEA
Washington to Seattle
- Flights
- 1,094
- Period
- July 2025 to June 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 77.6%. The late ones land a little over an hour behind schedule. That rests on 1,094 DCA to SEA flights, of which Alaska Airlines flew 729 at 76.7% on time.
Best time to fly DCA to SEA: a 8am–11am departure, ideally on a Saturday. Flights in that window arrived on time 80.0% of the time and Saturday flights 83.8%, against 73.2% for the route overall.
The national on-time rate over the same period is 77.6%, so this route runs 4 points behind the country as a whole. Across a thousand flights that is about 44 extra late arrivals.
Key figures
On time
73.2%
Arrivals under 15 minutes late, of 1,071 completed flights
Avg delay
70 min
Across delayed arrivals only, not all flights
Cancelled
1.74%
National rate is 1.81%
Best carrier
Alaska
76.7% on time across 729 flights
These figures cover 1,094 flights between July 2025 and June 2026. Beyond the headline rate, 8.6% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Which airline is most reliable on DCA to SEA
The choice of carrier is not cosmetic here. Alaska Airlines arrives on time 76.7% of the time; Delta Air Lines manages 66.1%. Sample sizes sit next to every figure, because a two-point gap across 365 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Alaska Airlines | 729 | 76.7% | 54 min | 1.10% | B |
| Delta Air Lines | 365 | 66.1% | 92 min | 3.01% | C− |
Delta Air Lines cancels 3.0% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
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.
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 5 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 | 79.2% | 79.7% | 0.58% | 11am–2pm, Sat | UA 326 17:55 |
| 2. DCA → SEAWashington to Seattle | Alaska Airlines | 75.9% | 76.7% | 1.10% | 8am–11am, Sat | AS 1 08:00 |
| 3. IAD → SEAWashington to Seattle | Alaska Airlines | 72.8% | 73.7% | 1.20% | 8am–11am, Thu | AS 351 07:00 |
| 4. BWI → SEABaltimore to Seattle | Alaska Airlines | 68.2% | 68.8% | 0.83% | 8am–11am, Sun | AS 379 19:10 |
| 5. DCA → SEAWashington to Seattle | Delta Air Lines | 64.1% | 66.1% | 3.01% | 2pm–5pm, Sat | — |
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 matters more here than the choice of carrier. The gap between the best and worst window is 11 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am365 flights80.0%
- 11am–2pm—
- 2pm–5pm183 flights69.5%
- 5pm–8pm546 flights69.9%
- 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 80.0% of the time, against 69.5% for the afternoon window. That is 11 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 546 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 41 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 85.7% in August. 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 83.8% on time and Wednesday the weakest at 68.4%. 15 points is a smaller lever than departure hour, but it is free.
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 20,000 reported delay minutes.
- 34%National Airspace System
- 29%Late-arriving aircraft
- 29%Carrier
- 8%Extreme weather
34% 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 6,849 minutes out of 20,000, against a national NAS share of 21%. The split is drawn from 20,062 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 80.0% on time here.
Cancellations sit at 1.74% against a national 1.81%, which is ordinary. Diversions add another 0.37%.
Connections and stage length
What a delay here actually costs
8.6% of arrivals land an hour or more late, close to the national 8.1%. 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 a little over 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 81.6% on time across 1,094 flights, 8 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 8 points of difference.
One caution: this is a thin sample. 1,094 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. 1,094 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 73.2% 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 26.8% of the 1,094 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on DCA to SEA?
Alaska Airlines leads at 76.7% on time across 729 flights. Delta Air Lines is at the other end on 66.1%, a gap of 11 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on DCA to SEA?
The 8am–11am departure window is the strongest at 80.0% on time. The 2pm–5pm window is the weakest at 69.5%, 11 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 85.7% in August. Across the year that is 41 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 SEA76.7%
- Delta Air Lines on DCA to SEA66.1%
- DCA to BOS, a related route71.4%
- LAX to SEA, a related route85.4%
- DCA to ORD, a related route74.3%
- Alaska Airlines on-time record76.7%
- Delta Air Lines on-time record66.1%
- Same route, different airline: where the carrier you pick matters most
- The best time of day to fly, according to 7.04 million flight records
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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.