Carrier route record
UASEA→IAD
United Airlines · Seattle to Washington
- Flights
- 626
- Period
- September 2025 to August 2026
- Share of route
- 34%
- Carriers
- 3
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with United Airlines.
United on SEA to IAD earns an A+. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 14 points better than the national rate of 77.3%. When something does go wrong the average delay runs a little over an hour. That rests on 626 flights, with a median arrival 17 minutes early.
Set against the rest of the country, United's SEA to IAD record is 14 points better than the US average of 77.3%. That gap is worth roughly 141 fewer late arrivals for every thousand flights.
Key figures
On time
91.4%
Arrivals under 15 minutes late, of 618 completed flights
Avg delay
76 min
Across delayed arrivals only, not all flights
Cancelled
0.64%
National rate is 1.89%
Whole route
84.8%
Every carrier on SEA to IAD, 1,822 flights
These figures cover 626 flights between September 2025 and August 2026. The median arrival is 17 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
United against every carrier on SEA to IAD
United flew 626 of the 1,822 flights on SEA to IAD, about 34% of it. Its 91.4% on time is 7 points better than the route as a whole, which runs 84.8%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from United at 91.4% to Delta at 76.7%. 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) | 626 | 91.4% | 76 min | 0.64% | A+ |
| Alaska Airlines | 835 | 83.3% | 38 min | 0.36% | B+ |
| Delta Air Linesthin sample | 361 | 76.7% | 80 min | 1.11% | B |
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Departure window
When United 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 626 flights.
- 5am–8am—
- 8am–11am361 flights93.3%
- 11am–2pm126 flights90.4%
- 2pm–5pm—
- 5pm–8pm—
- 8pm–5am139 flights87.5%
Scale runs 80% to 100%. Rows with fewer than 30 flights show a dash.
The early departures do better, though not dramatically: 93.3% on time for the 8am–11am window against 87.5% for 8pm–5am. Worth taking if the schedule allows, not worth an extra connection. 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 84.8% on time, 12 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 89 flights.
Across the week, Tuesday is the strongest day at 96.1% on time and Thursday the weakest at 86.3%, a spread of 10 points.
Arrival by arrival
How late United on SEA to IAD runs when it is late
United on SEA to IAD often beats the schedule: 363 of 618 completed flights, 59%, arrived 15 minutes or more early. The 53 late arrivals split 21 under half an hour, 11 between 30 and 60 minutes, and 21 an hour or more.
- 15+ min early363 flights58.7%
- Within 15 min202 flights32.7%
- 15–29 min late21 flights3.4%
- 30–59 min late11 flights1.8%
- 1–2 hours late15 flights2.4%
- 2+ hours late6 flights1.0%
Scale runs 0% to 100%.
Share of 618 completed flights by arrival against schedule.
16 of 54 late departures made up the time and arrived on time, 30% of them. 15 flights left on time and still arrived late.
The worst days
Worst days for United on SEA to IAD
The latest arrival of the period was on 5 July 2026, 15 hours 46 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The five worst days are spread across July, October, August and June, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 5 July 2026 | 15 hours 46 minutes | Carrier |
| 4 July 2026 | 3 hours 54 minutes | Carrier |
| 26 October 2025 | 3 hours 42 minutes | Late-arriving aircraft |
| 9 August 2026 | 2 hours 55 minutes | Late-arriving aircraft |
| 11 June 2026 | 2 hours 11 minutes | National Airspace System |
Delay causes
Why United runs late on this route
Carrier accounts for 50% of the 4,048 delay minutes carriers reported here, and the remaining four split what is left.
- 50%Carrier
- 32%Late-arriving aircraft
- 18%National Airspace System
- 0%Extreme weather
The largest share of delay minutes, 50%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 2,023 of the 4,048 delay minutes reported here. The split is drawn from 4,048 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 93.3% on time here.
Cancellations are rare at 0.64%, 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 costs
Badly late arrivals are rare here: only 3.4% 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 2,305 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 81.3% on time across 625 flights, 10 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 10 points of difference.
One caution: this is a thin sample. 626 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. 626 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 91.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 618 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 IAD83.3%
- Delta Air Lines on SEA to IAD76.7%
- United Airlines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- Washington Dulles International (IAD) 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.