Carrier route record
DLSEA→DCA
Delta Air Lines · Seattle to Washington
- Flights
- 365
- Period
- July 2025 to June 2026
- Share of route
- 33%
- Carriers
- 2
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.
Delta on SEA to DCA earns an A−. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 15 points better than the national rate of 77.6%. When something does go wrong the average delay runs about 2.1 hours. That rests on 365 flights, with a median arrival 12 minutes early.
Set against the rest of the country, Delta's SEA to DCA record is 15 points better than the US average of 77.6%. That gap is worth roughly 145 fewer late arrivals for every thousand flights.
Key figures
On time
92.1%
Arrivals under 15 minutes late, of 353 completed flights
Avg delay
126 min
Across delayed arrivals only, not all flights
Cancelled
3.01%
National rate is 1.81%
Whole route
81.6%
Every carrier on SEA to DCA, 1,094 flights
These figures cover 365 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
Delta against every carrier on SEA to DCA
Delta flew 365 of the 1,094 flights on SEA to DCA, about 33% of it. Its 92.1% on time is 11 points better than the route as a whole, which runs 81.6%. Ranked by on-time rate it is first 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.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines (this page) | 365 | 92.1% | 126 min | 3.01% | A− |
| Alaska Airlines | 729 | 76.4% | 58 min | 1.10% | B |
Flight by flight
Delta flight numbers on SEA to DCA
Departure window
When Delta runs best on this route
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 365 flights.
There are not enough flights in each departure window to split Delta's SEA to DCA record by time of day without the percentages moving on noise. The headline rate of 92.1% is the reliable figure here.
Across the year
Delta on SEA to DCA through the year
- Jul–Sep 202592 flights85.2%
- Oct–Dec 202592 flights91.1%
- Jan–Mar 202690 flights96.5%
- Apr–Jun 202691 flights95.6%
Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.
Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 92.1% on time across 365 flights.
Delta on SEA to DCA did not run the same all year. Its best quarter was Jan–Mar 2026 at 96.5% on time and its weakest Jul–Sep 2025 at 85.2%, a swing of 11 points on roughly 91 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
Across the week, Saturday is the strongest day at 98.0% on time and Thursday the weakest at 76.0%. 22 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Delta runs late on this route
One category carries most of the weight here. Carrier accounts for 86% of the 3,528 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.
- 86%Carrier
- 9%National Airspace System
- 3%Late-arriving aircraft
- 2%Security
The largest share of delay minutes, 86%, 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 3,036 of the 3,528 delay minutes reported here. The split is drawn from 3,528 reported delay minutes.
Cancellations run at 3.01%, against 1.81% nationally. That is roughly one flight in 30 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
Connections and stage length
What a delay here costs
Badly late arrivals are rare here: only 3.4% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
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 66.1% on time across 365 flights, 26 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 26 points of difference.
One caution: this is a thin sample. 365 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 Delta on SEA to DCA
Put together: the delay figures matter less here than the 3.01% cancellation rate. A late arrival costs you about 2.1 hours; a cancelled flight costs you the day. Book the 5am–8am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 353 completed flights over 12 months sit behind that.
Related
Where to go next
- SEA to DCA, every carrier
- Delta on DCA to SEA, the return leg
- Alaska Airlines on SEA to DCA76.4%
- Delta Air Lines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- Ronald Reagan Washington National (DCA) delay statistics
- The US routes with the most cancellations
- What a cancellation rate actually tells you (and what it hides)
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.