Route reliability record
SEA→RDU
Seattle to Raleigh
- Flights
- 918
- Period
- September 2025 to August 2026
- Distance
- 2,354 mi
- Carriers
- 2
This route lands a B+, 4 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about 45 minutes on average. That rests on 918 SEA to RDU flights, with a median arrival 6 minutes early.
Best time to fly SEA to RDU: a 8am–11am departure, ideally on a Wednesday. Flights in that window arrived on time 85.3% of the time and Wednesday flights 86.9%, against 81.4% for the route overall.
Set against the rest of the country, this route's record is 4 points better than the US average of 77.3%. That gap is worth roughly 41 fewer late arrivals for every thousand flights.
Key figures
On time
81.4%
Arrivals under 15 minutes late, of 908 completed flights
Avg delay
44 min
Across delayed arrivals only, not all flights
Cancelled
0.76%
National rate is 1.89%
Best carrier
Alaska
84.5% on time across 554 flights
These figures cover 918 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
Which airline is most reliable on SEA to RDU
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 Linesthin sample | 364 | 76.5% | 50 min | 1.37% | B |
Flight by flight
Flights on SEA to RDU
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Departure window
The best time of day to leave
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 918 flights.
- 5am–8am—
- 8am–11am364 flights85.3%
- 11am–2pm—
- 2pm–5pm349 flights76.7%
- 5pm–8pm—
- 8pm–5am205 flights82.4%
Scale runs 70% to 90%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 85.3% of the time, against 76.7% for the afternoon window. That is 9 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 364 flights scheduled in it.
Explore
Filter SEA to RDU by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On SEA to RDU, the best departure window is 8am–11am at 85.3% on time and the worst is 2pm–5pm at 76.7%, a real gap of 8.6 points. All US flights leaving 8am–11am ran 83.9%.
- 5–8am—
- 8–11am85.3%
- 11am–2pm—
- 2–5pm76.7%
- 5–8pm—
- 8pm–5am82.4%
best all US flightsScale 60% to 95%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 14 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
July is the worst month at 74.4% on time, 14 points below January, the best at 88.7%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. May was the busiest month here, with 93 flights.
Across the week, Wednesday is the strongest day at 86.9% on time and Monday the weakest at 76.5%, a spread of 10 points.
Delay causes
Why this route gets delayed
Carrier accounts for 44% of the 7,490 delay minutes carriers reported here, and the remaining four split what is left.
- 44%Carrier
- 29%Late-arriving aircraft
- 25%National Airspace System
- 2%Extreme weather
The largest share of delay minutes, 44%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 3,311 of the 7,490 delay minutes reported here. The split is drawn from 7,490 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 85.3% on time here.
Cancellations are rare at 0.76%, below the national 1.89% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 3.9% 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 78.0% on time across 918 flights, 3 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 3 points of difference.
One caution: this is a thin sample. 918 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.
Work out the risk of missing a connection in RDU after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 918 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 81.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 908 completed flights over 12 months sit behind that.
Common questions
SEA to RDU questions
How often is SEA to RDU delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.6% of the 918 flights in this analysis, against 22.7% nationally. Delayed flights are late by about 45 minutes on average.
How reliable is SEA to RDU compared with the rest of the country?
81.4% of flights arrive on time here against a national 77.3%, a difference of 4 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on SEA to RDU?
The 8am–11am departure window is the strongest at 85.3% on time. The 2pm–5pm window is the weakest at 76.7%, 9 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are July delays on SEA to RDU?
July is the weakest month at 74.4% on time, compared with 88.7% in January. Across the year that is 14 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- RDU to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Raleigh-Durham International (RDU) delay statistics
- Alaska Airlines on SEA to RDU84.5%
- Delta Air Lines on SEA to RDU76.5%
- SEA to LAX, a related route82.0%
- ATL to RDU, a related route80.0%
- SEA to PHX, a related route78.2%
- Alaska Airlines on-time record84.5%
- Delta Air Lines on-time record76.5%
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. SEA to RDU and RDU to SEA are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.