Carrier route record
DLSEA→RDU
Delta Air Lines · Seattle to Raleigh
- 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 SEA to RDU lands a B, about a point worse than the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about 50 minutes on average. That rests on 364 flights, with a median arrival 4 minutes early.
The US average over the same twelve months is 77.3%, 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.
Key figures
On time
76.5%
Arrivals under 15 minutes late, of 358 completed flights
Avg delay
50 min
Across delayed arrivals only, not all flights
Cancelled
1.37%
National rate is 1.89%
Whole route
81.4%
Every carrier on SEA to RDU, 918 flights
These figures cover 364 flights between September 2025 and August 2026. The median arrival is 4 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 SEA to RDU
Delta flew 364 of the 918 flights on SEA to RDU, about 40% of it. Its 76.5% on time is 5 points worse than the route as a whole, which runs 81.4%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from Alaska at 84.5% to Delta at 76.5%.
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 |
|---|---|---|---|---|---|
| Alaska Airlines | 554 | 84.5% | 38 min | 0.36% | B+ |
| Delta Air Lines (this page)thin sample | 364 | 76.5% | 50 min | 1.37% | B |
Flight by flight
Delta flight numbers on SEA to RDU
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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 SEA to RDU record by time of day without the percentages moving on noise. The headline rate of 76.5% is the reliable figure here.
Across the year
Delta on SEA to RDU through the year
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, Saturday is the strongest day at 84.0% on time and Monday the weakest at 66.7%, a spread of 17 points.
Arrival by arrival
How late Delta on SEA to RDU runs when it is late
Delta on SEA to RDU often beats the schedule: 92 of 358 completed flights, 26%, arrived 15 minutes or more early. Most of the lateness is short. 42 of the 84 late arrivals were under half an hour behind, and 22 reached an hour or more.
- 15+ min early92 flights25.7%
- Within 15 min182 flights50.8%
- 15–29 min late42 flights11.7%
- 30–59 min late20 flights5.6%
- 1–2 hours late15 flights4.2%
- 2+ hours late7 flights2.0%
Scale runs 0% to 100%.
Share of 358 completed flights by arrival against schedule.
16 of 66 late departures made up the time and arrived on time, 24% of them. In the other direction, 34 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 RDU.
The worst days
Worst days for Delta on SEA to RDU
The latest arrival of the period was on 14 June 2026, 4 hours 27 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. On three of the five worst days the largest share was filed as carrier-caused (crew, maintenance, fuelling, baggage).
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 14 June 2026 | 4 hours 27 minutes | Late-arriving aircraft |
| 16 April 2026 | 3 hours 3 minutes | Carrier |
| 26 January 2026 | 2 hours 53 minutes | Carrier |
| 2 February 2026 | 2 hours 23 minutes | Late-arriving aircraft |
| 18 May 2026 | 2 hours 23 minutes | Carrier |
Delay causes
Why Delta runs late on this route
Carrier accounts for 51% of the 4,223 delay minutes carriers reported here, and the remaining four split what is left.
- 51%Carrier
- 25%Late-arriving aircraft
- 24%National Airspace System
- 0%Extreme weather
The largest share of delay minutes, 51%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,134 of the 4,223 delay minutes reported here. The split is drawn from 4,223 reported delay minutes.
Cancellations sit at 1.37% against a national 1.89%, which is ordinary. Diversions add another 0.27%.
Connections and stage length
What a delay here costs
6.1% of arrivals land an hour or more late, close to the national 8.3%, so 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 82.8% 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 76.5% 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.
Related
Where to go next
- SEA to RDU, every carrier
- Delta on RDU to SEA, the return leg
- Alaska Airlines on SEA to RDU84.5%
- Delta Air Lines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- Raleigh-Durham International (RDU) delay statistics
- Worst months to fly in the US, ranked by the data
- The best day of the week to fly, and why it is the second lever
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.