Route reliability record
SEA→DCA
Seattle to Washington
- Flights
- 1,094
- Period
- July 2025 to June 2026
- Distance
- 2,329 mi
- Carriers
- 2
This route lands a B, 4 points better than the national rate of 77.6%. Roughly one flight in five 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 1,094 SEA to DCA flights, of which Delta Air Lines flew 365 at 92.1% on time.
Best time to fly SEA to DCA: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 92.1% of the time and Saturday flights 90.1%, against 81.6% for the route overall.
Set against the rest of the country, this route's record is 4 points better than the US average of 77.6%. That gap is worth roughly 40 fewer late arrivals for every thousand flights.
Key figures
On time
81.6%
Arrivals under 15 minutes late, of 1,062 completed flights
Avg delay
68 min
Across delayed arrivals only, not all flights
Cancelled
1.74%
National rate is 1.81%
Best carrier
Delta
92.1% on time across 365 flights
These figures cover 1,094 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
Which airline is most reliable on SEA to DCA
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 92.1% of the time; Alaska Airlines manages 76.4%. Sample sizes sit next to every figure, because a two-point gap across 729 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 365 | 92.1% | 126 min | 3.01% | A− |
| Alaska Airlines | 729 | 76.4% | 58 min | 1.10% | B |
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 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.
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 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SEA → DCASeattle to Washington | Delta Air Lines | 89.3% | 92.1% | 3.01% | 5am–8am, Sat | DL 786 07:20 |
| 2. SEA → IADSeattle to Washington | United Airlines | 85.9% | 86.5% | 0.72% | 8am–11am, Tue | — |
| 3. SEA → BWISeattle to Baltimore | Alaska Airlines | 82.4% | 82.8% | 0.50% | 8pm–5am, Sat | AS 378 10:11 |
| 4. SEA → IADSeattle to Washington | Alaska Airlines | 80.1% | 80.4% | 0.36% | 8pm–5am, Wed | AS 367 23:30 |
| 5. SEA → DCASeattle to Washington | Alaska Airlines | 75.6% | 76.4% | 1.10% | 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 29 points, against 16 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am365 flights92.1%
- 8am–11am365 flights85.9%
- 11am–2pm137 flights73.0%
- 2pm–5pm227 flights63.3%
- 5pm–8pm—
- 8pm–5am—
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 92.1% of the time, against 63.3% for the afternoon window. That is 29 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 365 flights scheduled in it.
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 90.1% on time and Thursday the weakest at 75.0%. 15 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. National Airspace System accounts for 45% of the 13,000 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.
- 45%National Airspace System
- 37%Carrier
- 10%Late-arriving aircraft
- 8%Extreme weather
- 1%Security
The largest share of delay minutes, 37%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 4,880 of the 13,000 delay minutes reported here. The split is drawn from 13,204 reported delay minutes.
45% 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 5,942 minutes out of 13,000, against a national NAS share of 21%.
Cancellations sit at 1.74% against a national 1.81%, which is ordinary. Diversions add another 1.19%.
Connections and stage length
What a delay here actually costs
6.2% 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 is a different operation and performs like one: it runs 73.2% on time across 1,094 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. 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 DCA 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 81.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,062 completed flights over 12 months sit behind that.
Common questions
SEA to DCA questions
How often is SEA to DCA delayed?
Roughly one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.4% of the 1,094 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SEA to DCA?
Delta Air Lines leads at 92.1% on time across 365 flights. Alaska Airlines is at the other end on 76.4%, a gap of 16 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 SEA to DCA?
The 5am–8am departure window is the strongest at 92.1% on time. The 2pm–5pm window is the weakest at 63.3%, 29 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 DCA92.1%
- Alaska Airlines on SEA to DCA76.4%
- SEA to LAX, a related route83.4%
- BOS to DCA, a related route74.0%
- SEA to PHX, a related route79.2%
- Delta Air Lines on-time record92.1%
- Alaska Airlines on-time record76.4%
- 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. 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.