84% of flights from Seattle to Washington arrived on time over the past 12 months. That is better than the typical U.S. route. The 1 p.m. departures ran on time 90% of the time; the 4 p.m. ones 78%. Most reliable airline: United Airlines (90%). 5% of flights arrived more than an hour late or not at all.
How late?
The on-time rate treats a flight 20 minutes late the same as one 5 hours late. Here's the split for SEA → IAD: when a flight was late, it was under 45 minutes late 64% of the time. About 1 in 25 flights landed an hour or more late, and 1 in 202 three hours or more; 0.6% were cancelled outright.
- On time or early84%
- 15–30 min late6.6%
- 30–60 min late4.3%
- 1–2 hours late2.7%
- 2–3 hours late0.8%
- 3+ hours late0.5%
- Diverted0.5%
- Cancelled0.6%
Share of all 1,822 scheduled flights, past 12 months, by arrival time against schedule.
By airline
| Airline | Flights | On time | Cancelled | Typical arrival | 1h+ late | Avg when late | Operated by |
|---|---|---|---|---|---|---|---|
| Alaska Airlines | 835 | 83% | 0.4% | −8 min | 1.9% | +38 min | Alaska Airlines |
| United Airlines | 626 | 90% | 0.6% | −17 min | 3.4% | +76 min | United Airlines |
| Delta Air Lines | 361 | 76% | 1.1% | −6 min | 10.2% | +80 min | Delta Air Lines |
Airline = the name on the ticket. Regional flights (e.g. "Delta Connection") count under the ticketing airline, and the operator is listed.
Best time of day to fly
On-time rate by scheduled departure hour (local time at SEA). Delays build through the day as late planes knock on, so early flights usually do best.
By airline and hour
| Departs | Alaska Airlines | United Airlines | Delta Air Lines |
|---|---|---|---|
| 8 a.m. | 82% | 92% | — |
| 9 a.m. | 82% | — | — |
| 1 p.m. | — | 90% | — |
| 3 p.m. | — | — | 76% |
| 4 p.m. | 80% | — | 76% |
| 10 p.m. | 77% | — | — |
| 11 p.m. | — | 83% | — |
Last flight of the day
On SEA → IAD, each airline's last flight of the day was cancelled 0.6% of the time, against 0.3% for its earlier flights (2.3× as often). It arrived 3+ hours late 0.2% of the time (earlier flights: 0.1%). It matters more than the numbers suggest. Miss an earlier flight and there's another one that evening; miss the last one and you're usually waiting until morning.
| Airline | Last departure | Last: cancelled | Last: 3h+ late | Earlier: cancelled | Next morning |
|---|---|---|---|---|---|
| Alaska Airlines | 10:43 p.m. | 0.0% | 0.0% | 0.4% | first flight 9:13 a.m. |
| United Airlines | 11:20 p.m. | 1.6% | 0.5% | 0.0% | first flight 8:15 a.m. |
Last flight = the airline's last scheduled departure on this route that day, on days it flies the route at least twice; past 12 months. Times are typical scheduled times over the latest three months.
If you need to be in IAD tonight, book an earlier flight so there's a backup if it's cancelled.
By month
Each calendar month pooled over 2023–2026. Best: October (88%). Worst: January (72%).
By day of week
| Day | Flights | On time | Cancelled |
|---|---|---|---|
| Monday | 273 | 82% | 0.0% |
| Tuesday | 240 | 85% | 0.4% |
| Wednesday | 250 | 90% | 0.0% |
| Thursday | 270 | 82% | 0.7% |
| Friday | 276 | 82% | 1.1% |
| Saturday | 242 | 84% | 0.0% |
| Sunday | 271 | 82% | 1.8% |
Why flights were late
Share of delay minutes on flights 15+ minutes late, as reported to BTS by the airlines.
Cancellations: weather 9 · airline 2
Month by month
Flight numbers on this route
Regular flights with at least 120 scheduled trips in the past year. Sorted by departure time.
| Flight | Departs | Flights | On time | Cancelled | Typical arrival | Operated by |
|---|---|---|---|---|---|---|
| AS 737 | 9:13 a.m. | 237 | 81% | 0.4% | −7 min | Alaska Airlines |
| DL 541 | 3:20 p.m. | 349 | 75% | 1.1% | −6 min | Delta Air Lines |
| AS 406 | 4:01 p.m. | 125 | 81% | 0.8% | −8 min | Alaska Airlines |
| AS 367 | 10:43 p.m. | 284 | 83% | 0.0% | −7 min | Alaska Airlines |
Worst days in the past year
| Date | Flights | On time | Cancelled |
|---|---|---|---|
| Jan 25, 2026 | 3 | 0% | 3 |
| Mar 13, 2026 | 4 | 25% | 1 |
| Oct 27, 2025 | 4 | 25% | 0 |
| Nov 17, 2025 | 4 | 25% | 0 |
| Jul 16, 2026 | 7 | 29% | 0 |
Nearby airport alternatives
Other ways to make the same trip, using airports within 60 miles of Seattle or Washington. None has been clearly more reliable than SEA → IAD.
| Route | Flights | On time | Cancelled |
|---|---|---|---|
| SEA → IAD (this route) | 1,822 | 84% | 0.6% |
| SEA → DCA Seattle-Tacoma to Washington Reagan National | 1,092 | 81% | 1.4% |
| SEA → BWI Seattle-Tacoma to Baltimore/Washington | 719 | 80% | 0.7% |
Questions
How often are flights from SEA to IAD on time?
84% of 1,822 scheduled flights from Seattle, WA to Washington, DC arrived within 15 minutes of schedule between September 2025 and August 2026. 0.6% were cancelled.
What is the best time of day to fly SEA to IAD?
Flights scheduled to leave at 1 p.m. were the most reliable (90% on time). The 4 p.m. departures were the least (78%).
Which airline is most on time from SEA to IAD?
United Airlines: 90% of its 626 flights on the route arrived on time. Alaska Airlines: 83%. Delta Air Lines: 76%.
What month has the most delays from SEA to IAD?
January (72% on time). The best month is October (88%), over 2023–2026.
Is the last flight of the day from SEA to IAD more likely to be cancelled?
Yes. Each airline's last SEA–IAD flight of the day was cancelled 0.6% of the time over the past year, against 0.3% for its earlier flights. If the last flight is cancelled, the next one is usually the following morning.
Related
- IAD → SEA (return)
- Seattle-Tacoma (SEA) delays by hour
- Flights into Washington Dulles (IAD)
- Alaska Airlines on-time record
- United Airlines on-time record
- Delta Air Lines on-time record
- Connecting off this flight? Check the risk
Domestic flights by the airlines that report to the U.S. DOT, plus their regional partners. "On time" means arriving less than 15 minutes after schedule; cancelled and diverted flights count as not on time. Past performance is a guide, not a forecast. Method.