Carrier route record

DLRDU→SEA

Delta Air Lines · Raleigh to Seattle

Flights: 364
Period: September 2025 to August 2026
Share of route: 40%
Carriers: 2

Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Delta Air Lines.

Delta on RDU to SEA lands a B, 6 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 roughly 50 minutes on average. That rests on 364 flights, with a median arrival 6 minutes early.

Set against the rest of the country, Delta's RDU to SEA record is 6 points better than the US average of 77.3%. That gap is worth roughly 55 fewer late arrivals for every thousand flights.

On time

82.8%

Arrivals under 15 minutes late, of 355 completed flights

Avg delay

49 min

Across delayed arrivals only, not all flights

Cancelled

1.37%

National rate is 1.89%

Whole route

78.0%

Every carrier on RDU to SEA, 918 flights

These figures cover 364 flights between September 2025 and August 2026. The median arrival is 6 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

Delta against every carrier on RDU to SEA

Delta flew 364 of the 918 flights on RDU to SEA, about 40% of it. Its 82.8% on time is 5 points better than the route as a whole, which runs 78.0%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from Delta at 82.8% to Alaska at 74.9%.

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 RDU to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines (this page)thin sample	364	82.8%	49 min	1.37%	B
Alaska Airlines	554	74.9%	52 min	1.08%	C

Flight by flight

Delta flight numbers on RDU to SEA

DL 35407:3683.5% · 348 flights

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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 364 flights.

There are not enough flights in each departure window to split Delta's RDU to SEA record by time of day without the percentages moving on noise. The headline rate of 82.8% is the reliable figure here.

Across the year

Delta on RDU to SEA through the year

Jul–Sep 202530 flights96.7%
Oct–Dec 202591 flights77.5%
Jan–Mar 202690 flights75.0%
Apr–Jun 202691 flights83.3%
Jul–Sep 202662 flights93.5%

Scale runs 65% to 100%.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 82.8% on time across 364 flights.

Delta on RDU to SEA did not run the same all year. Its best quarter was Jul–Sep 2025 at 96.7% on time and its weakest Jan–Mar 2026 at 75.0%, a swing of 22 points on roughly 73 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, Tuesday is the strongest day at 90.4% on time and Monday the weakest at 67.3%, a spread of 23 points.

Arrival by arrival

How late Delta on RDU to SEA runs when it is late

Delta on RDU to SEA often beats the schedule: 104 of 355 completed flights, 29%, arrived 15 minutes or more early. The 61 late arrivals split 27 under half an hour, 19 between 30 and 60 minutes, and 15 an hour or more.

15+ min early104 flights29.3%
Within 15 min190 flights53.5%
15–29 min late27 flights7.6%
30–59 min late19 flights5.4%
1–2 hours late9 flights2.5%
2+ hours late6 flights1.7%

Scale runs 0% to 100%.

Share of 355 completed flights by arrival against schedule.

9 of 39 late departures made up the time and arrived on time, 23% of them. In the other direction, 31 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SEA.

The worst days

Worst days for Delta on RDU to SEA

The latest arrival of the period was on 27 February 2026, 2 hours 58 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on five of the five worst days.

The latest arrivals of Delta on RDU to SEA in the period
Date	Arrived late by	Largest filed cause
27 February 2026	2 hours 58 minutes	Carrier
2 February 2026	2 hours 19 minutes	Carrier
12 January 2026	2 hours 8 minutes	Carrier
18 October 2025	2 hours 4 minutes	Carrier
10 November 2025	2 hours 3 minutes	Carrier

Delay causes

Why Delta runs late on this route

Carrier accounts for 53% of the 2,984 delay minutes carriers reported here, and the remaining four split what is left.

Carrier
53%
National Airspace System
45%
Late-arriving aircraft
2%
Extreme weather
1%

The largest share of delay minutes, 53%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,570 of the 2,984 delay minutes reported here. The split is drawn from 2,984 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 1,331 minutes out of 2,984, against a national NAS share of 21%.

Cancellations sit at 1.37% against a national 1.89%, which is ordinary. Diversions add another 1.10%.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 4.2% land an hour or more behind schedule, against 8.3% 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 2,354 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 76.5% on time across 364 flights, 6 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 6 points of difference.

One caution: this is a thin sample. 364 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 RDU to SEA

Put together: treat all of this as provisional. 364 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 82.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 355 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures