Carrier route record

DLSEA→RDU

Delta Air Lines · Seattle to Raleigh

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 SEA to RDU lands a B, about a point worse than the national rate of 77.6%. About one flight in four 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 5 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate Delta on SEA to RDU from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

76.8%

Arrivals under 15 minutes late, of 358 completed flights

Avg delay

49 min

Across delayed arrivals only, not all flights

Cancelled

1.37%

National rate is 1.81%

Whole route

78.6%

Every carrier on SEA to RDU, 919 flights

These figures cover 364 flights between July 2025 and June 2026. The median arrival is 5 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 RDU

Delta flew 364 of the 919 flights on SEA to RDU, about 40% of it. Its 76.8% on time is 2 points worse than the route as a whole, which runs 78.6%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from Alaska at 79.8% to Delta at 76.8%.

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 SEA to RDU
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlines	555	79.8%	40 min	0.90%	B+
Delta Air Lines (this page)thin sample	364	76.8%	49 min	1.37%	B

Flight by flight

Delta flight numbers on SEA to RDU

DL 48915:5576.6% · 360 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 SEA to RDU record by time of day without the percentages moving on noise. The headline rate of 76.8% is the reliable figure here.

Across the year

Delta on SEA to RDU through the year

Darker means more delays. Figures are on-time percentages.August best, April worst

Delays peak in April, when the on-time rate falls to 66.7%. August is the strongest month at 80.6%. Moving a flexible trip across that boundary buys 14 points. March was the busiest month here, with 31 flights.

Across the week, Tuesday is the strongest day at 83.0% on time and Sunday the weakest at 70.6%. 12 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 53% of the 4,094 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
53%
National Airspace System
24%
Late-arriving aircraft
22%
Extreme weather
0%

The largest share of delay minutes, 53%, 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 2,174 of the 4,094 delay minutes reported here. The split is drawn from 4,094 reported delay minutes.

Cancellations sit at 1.37% against a national 1.81%, which is ordinary. Diversions add another 0.27%.

Connections and stage length

What a delay here costs

5.9% 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 50 minutes, which a normal layover absorbs.

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 83.1% on time across 364 flights, 6 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 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 SEA to RDU

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 76.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 358 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