Carrier route record

DLRDU→SEA

Delta Air Lines · Raleigh to Seattle

Flights: 364
Period: July 2025 to June 2026
Share of route: 40%
Carriers: 2

Historical statistics for July 2025 to June 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 77.6%. About one flight in six arrives 15 minutes late or worse, and those flights are late by about 50 minutes on average. That is a workable record, not a spotless one. 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 77.6%. That gap is worth roughly 55 fewer late arrivals for every thousand flights.

On time

83.1%

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 1.81%

Whole route

75.9%

Every carrier on RDU to SEA, 919 flights

These figures cover 364 flights between July 2025 and June 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.

Carrier by carrier

Delta against every carrier on RDU to SEA

Delta flew 364 of the 919 flights on RDU to SEA, about 40% of it. Its 83.1% on time is 7 points better than the route as a whole, which runs 75.9%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from Delta at 83.1% to Alaska at 71.1%.

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 RDU to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines (this page)thin sample	364	83.1%	49 min	1.37%	B
Alaska Airlines	555	71.1%	47 min	1.62%	C

Flight by flight

Delta flight numbers on RDU to SEA

DL 35407:1183.8% · 348 flights

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 83.1% is the reliable figure here.

Across the year

Delta on RDU to SEA through the year

Jul–Sep 202592 flights95.7%
Oct–Dec 202591 flights77.5%
Jan–Mar 202690 flights75.0%
Apr–Jun 202691 flights83.3%

Scale runs 65% 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 83.1% 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 95.7% on time and its weakest Jan–Mar 2026 at 75.0%, a swing of 21 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, Thursday is the strongest day at 88.0% on time and Monday the weakest at 70.6%. 17 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 52% of the 2,941 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.

Carrier
52%
National Airspace System
43%
Late-arriving aircraft
3%
Extreme weather
1%

The largest share of delay minutes, 52%, 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 1,533 of the 2,941 delay minutes reported here. The split is drawn from 2,941 reported delay minutes.

43% 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 1,276 minutes out of 2,941, against a national NAS share of 21%.

Cancellations sit at 1.37% against a national 1.81%, 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 8.1% 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 2,354 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 76.8% 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 83.1% 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures