Carrier route record

DLDCA→SEA

Delta Air Lines · Washington to Seattle

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 DCA to SEA draws a C−. About one flight in three arrives at least 15 minutes late, and the typical late arrival is an hour and a half behind schedule. Build slack into anything you connect to. That rests on 365 flights, with a median arrival 2 minutes early.

The national on-time rate over the same period is 77.6%, so Delta on DCA to SEA runs 12 points behind the country as a whole. Across a thousand flights that is about 115 extra late arrivals.

On time

66.1%

Arrivals under 15 minutes late, of 354 completed flights

Avg delay

92 min

Across delayed arrivals only, not all flights

Cancelled

3.01%

National rate is 1.81%

Whole route

73.2%

Every carrier on DCA to SEA, 1,094 flights

These figures cover 365 flights between July 2025 and June 2026. Beyond the headline rate, 14.1% 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

Delta against every carrier on DCA to SEA

Delta flew 365 of the 1,094 flights on DCA to SEA, about 33% of it. Its 66.1% on time is 7 points worse than the route as a whole, which runs 73.2%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from Alaska at 76.7% to Delta at 66.1%.

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.

On-time performance by carrier on DCA to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlines	729	76.7%	54 min	1.10%	B
Delta Air Lines (this page)	365	66.1%	92 min	3.01%	C−

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.

5am–8am—
8am–11am—
11am–2pm—
2pm–5pm183 flights69.5%
5pm–8pm182 flights62.7%
8pm–5am—

Scale runs 55% to 75%. Rows with fewer than 30 flights show a dash.

The best window here is not the first bank but the 2pm–5pm slot at 69.5% on time, ahead of 5pm–8pm at 62.7%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 2pm–5pm window is the busiest, with 183 flights scheduled in it.

Across the year

Delta on DCA to SEA through the year

Jul–Sep 202592 flights65.2%
Oct–Dec 202592 flights61.1%
Jan–Mar 202690 flights64.7%
Apr–Jun 202691 flights73.3%

Scale runs 55% to 80%. 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 66.1% on time across 365 flights.

Delta on DCA to SEA did not run the same all year. Its best quarter was Apr–Jun 2026 at 73.3% on time and its weakest Oct–Dec 2025 at 61.1%, a swing of 12 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 78.8% on time and Thursday the weakest at 59.2%. 20 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

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 11,000 reported delay minutes.

Carrier
37%
Late-arriving aircraft
32%
National Airspace System
25%
Extreme weather
6%

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 4,087 of the 11,000 delay minutes reported here. The split is drawn from 11,000 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

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 14.1% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

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 92.1% on time across 365 flights, 26 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 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 DCA to SEA

Put together: the delay figures matter less here than the 3.01% cancellation rate. A late arrival costs you an hour and a half; a cancelled flight costs you the day. Book the 2pm–5pm departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 354 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures