Carrier route record
UASEA→IAD
United Airlines · Seattle to Washington
- Flights
- 690
- Period
- July 2025 to June 2026
- Share of route
- 37%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on SEA to IAD earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.6%. When something does go wrong the average delay runs a little over an hour. That rests on 690 flights, with a median arrival 13 minutes early.
Set against the rest of the country, United's SEA to IAD record is 9 points better than the US average of 77.6%. That gap is worth roughly 89 fewer late arrivals for every thousand flights.
Key figures
On time
86.5%
Arrivals under 15 minutes late, of 680 completed flights
Avg delay
79 min
Across delayed arrivals only, not all flights
Cancelled
0.72%
National rate is 1.81%
Whole route
81.9%
Every carrier on SEA to IAD, 1,886 flights
These figures cover 690 flights between July 2025 and June 2026. The median arrival is 13 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
United against every carrier on SEA to IAD
United flew 690 of the 1,886 flights on SEA to IAD, about 37% of it. Its 86.5% on time is 5 points better than the route as a whole, which runs 81.9%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from United at 86.5% to Delta at 77.0%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
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 |
|---|---|---|---|---|---|
| United Airlines (this page) | 690 | 86.5% | 79 min | 0.72% | A+ |
| Alaska Airlines | 835 | 80.4% | 41 min | 0.36% | B+ |
| Delta Air Linesthin sample | 361 | 77.0% | 75 min | 1.11% | B |
Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 17 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am361 flights92.4%
- 11am–2pm134 flights87.1%
- 2pm–5pm—
- 5pm–8pm—
- 8pm–5am195 flights75.0%
Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 92.4% of the time, against 75.0% for the overnight window. That is 17 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 361 flights scheduled in it.
Across the year
United on SEA to IAD through the year
August is the worst month at 71.1% on time, 26 points below January, the best at 97.1%. 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. July was the busiest month here, with 122 flights.
Across the week, Tuesday is the strongest day at 92.3% on time and Saturday the weakest at 80.9%. 11 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 51% of the 7,291 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.
- 51%Late-arriving aircraft
- 36%Carrier
- 12%National Airspace System
- 1%Extreme weather
51% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 7,291 reported delay minutes here, that single category outweighs weather by 51 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 7,291 reported delay minutes.
The largest share of delay minutes, 36%, 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 2,641 of the 7,291 delay minutes reported here.
Cancellations are rare at 0.72%, below the national 1.81% 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 costs
6.0% 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 a little over an hour, which a normal layover absorbs.
At 2,305 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 79.7% on time across 688 flights, 7 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 7 points of difference.
One caution: this is a thin sample. 690 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 United on SEA to IAD
Put together: treat all of this as provisional. 690 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 86.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 680 completed flights over 12 months sit behind that.
Related
Where to go next
- SEA to IAD, every carrier
- United on IAD to SEA, the return leg
- Alaska Airlines on SEA to IAD80.4%
- Delta Air Lines on SEA to IAD77.0%
- United Airlines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- Washington Dulles International (IAD) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.