Route reliability record
SEA→DCA
Seattle to Washington
- Flights
- 1,092
- Period
- September 2025 to August 2026
- Distance
- 2,329 mi
- Carriers
- 2
This route lands a B, 5 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 about an hour on average. That rests on 1,092 SEA to DCA flights, with a median arrival 13 minutes early.
Best time to fly SEA to DCA: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 91.8% of the time and Saturday flights 91.3%, against 82.6% for the route overall.
Set against the rest of the country, this route's record is 5 points better than the US average of 77.3%. That gap is worth roughly 53 fewer late arrivals for every thousand flights.
Key figures
On time
82.6%
Arrivals under 15 minutes late, of 1,067 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
1.37%
National rate is 1.89%
Best carrier
Alaska
78.0% on time across 728 flights
These figures cover 1,092 flights between September 2025 and August 2026. The median arrival is 13 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
Which airline is most reliable on SEA to DCA
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 |
|---|---|---|---|---|---|
| Delta Air Linesthin sample | 364 | 91.8% | 119 min | 2.75% | A |
| Alaska Airlines | 728 | 78.0% | 54 min | 0.69% | B+ |
Flight by flight
Flights on SEA to DCA
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 Seattle to Washington
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. SEA → IADSeattle to Washington | United Airlines | 90.8% | 91.4% | 0.64% | 8am–11am, Tue | — |
| 2. SEA → BWISeattle to Baltimore | Alaska Airlines | 84.2% | 84.8% | 0.67% | 8pm–5am, Sat | AS 378 09:03 |
| 3. SEA → IADSeattle to Washington | Alaska Airlines | 83.0% | 83.3% | 0.36% | 8am–11am, Wed | AS 367 22:43 |
| 4. SEA → DCASeattle to Washington | Alaska Airlines | 77.5% | 78.0% | 0.69% | 8am–11am, Sat | AS 4 08:00 |
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 24 points, against half a point between the best and worst carrier.
- 5am–8am364 flights91.8%
- 8am–11am364 flights85.2%
- 11am–2pm186 flights68.3%
- 2pm–5pm178 flights73.2%
- 5pm–8pm—
- 8pm–5am—
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
The weak window here is the middle of the day, not the evening: 11am–2pm runs 68.3% on time against 91.8% for 5am–8am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 5am–8am window is the busiest, with 364 flights scheduled in it.
Explore
Filter SEA to DCA 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 SEA to DCA, the best departure window is 5am–8am at 91.8% on time and the worst is 11am–2pm at 68.3%, a wide gap of 23.5 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am91.8%
- 8–11am85.2%
- 11am–2pm68.3%
- 2–5pm73.2%
- 5–8pm—
- 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 27 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.
May is the best month on the calendar at 91.4% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. January was the busiest month here, with 93 flights.
Across the week, Saturday is the strongest day at 91.3% on time and Thursday the weakest at 75.5%, a spread of 16 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 12,000 reported delay minutes.
- 42%National Airspace System
- 39%Carrier
- 12%Late-arriving aircraft
- 8%Extreme weather
- 1%Security
The largest share of delay minutes, 39%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 4,592 of the 12,000 delay minutes reported here. The split is drawn from 11,879 reported delay minutes.
42% 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 4,933 minutes out of 12,000, against a national NAS share of 21%.
Cancellations sit at 1.37% against a national 1.89%, which is ordinary. Diversions add another 0.92%.
Connections and stage length
What a delay here actually costs
5.4% 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 73.4% on time across 1,092 flights, 9 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 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 DCA 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 82.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,067 completed flights over 12 months sit behind that.
Common questions
SEA to DCA questions
How often is SEA to DCA delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 17.4% 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 SEA to DCA compared with the rest of the country?
82.6% of flights arrive on time here against a national 77.3%, a difference of 5 points in its favour. That is worth a B on this site's grading scale.
What time of day has the fewest delays on SEA to DCA?
The 5am–8am departure window is the strongest at 91.8% on time. The 11am–2pm window is the weakest at 68.3%, 24 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 September delays on SEA to DCA?
September is the weakest month at 64.0% on time, compared with 91.4% in May. Across the year that is 27 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
- DCA to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Ronald Reagan Washington National (DCA) delay statistics
- Delta Air Lines on SEA to DCA91.8%
- Alaska Airlines on SEA to DCA78.0%
- SEA to LAX, a related route82.0%
- BOS to DCA, a related route72.6%
- SEA to PHX, a related route78.2%
- Delta Air Lines on-time record91.8%
- Alaska Airlines on-time record78.0%
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. SEA to DCA and DCA to SEA 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.