IAD to SEA flight delays & on-time performance
Nonstop flights from Washington Dulles International Airport to Seattle–Tacoma International Airport · 2,305 miles · Aug 2025 – Jul 2026
No FAA-reported ground stops or delays at IAD or SEA right now. Individual flights can still be delayed by the airline; check with your airline for your flight.
Key facts
- Flights from Washington (IAD) to Seattle (SEA) arrived on time 78% of the time in Aug 2025 – Jul 2026, in line with the national average.
- 1% were cancelled, and 6% arrived an hour or more late.
- United Airlines was the most punctual airline here (81% on time); Alaska Airlines was the least (75%).
- Departures scheduled around 6am did best (93% on time); around 7pm did worst (54%).
- Saturday was the most reliable day to fly (80% on time) and Tuesday the least (74%).
- The largest source of delay minutes was airline (crew, maintenance, cleaning, fueling) (44%).
Which airline is most on time from IAD to SEA?
Ranked by on-time arrival rate. Regional airlines fly under their partner's brand (e.g. SkyWest for Delta Connection or United Express).
| Airline | On time | Cancelled | Avg delay | 1 hr+ late | Flights |
|---|---|---|---|---|---|
| United Airlines | 81% | 0.6% | 13 min | 5.2% | 655 |
| Delta Air Lines | 77% | 1.4% | 23 min | 7.6% | 361 |
| Alaska Airlines | 75% | 1.2% | 13 min | 5.9% | 835 |
Best time of day to fly
On-time arrival rate by scheduled departure hour (local time).
- 6am93%121 flights
- 7am75%567 flights
- 8am88%41 flights
- 9am88%264 flights
- 1pm90%165 flights
- 5pm75%382 flights
- 6pm65%237 flights
- 7pm54%57 flights
Best day of the week
On-time arrival rate by day of departure.
- Monday79%0.7% cancelled
- Tuesday74%0.8% cancelled
- Wednesday77%0.4% cancelled
- Thursday78%0.7% cancelled
- Friday78%0.4% cancelled
- Saturday80%1.2% cancelled
- Sunday78%2.9% cancelled
On-time trend by month
Why flights are late
Share of delay minutes by cause, as reported by airlines to the DOT.
- Airline (crew, maintenance, cleaning, fueling)44%
- Air traffic control & airport congestion32%
- Late-arriving aircraft14%
- Extreme weather8%
- Security1%
Why flights are cancelled
Share of cancellations by reason.
- Airline (crew, maintenance, cleaning, fueling)53%
- Extreme weather47%
- Air traffic control & airport congestion0%
- Security0%
IAD to SEA: common questions
- How often are IAD to SEA flights on time?
- 78% of flights arrived less than 15 minutes late in Aug 2025 – Jul 2026, compared with 78% for all US flights.
- How often are flights from Washington to Seattle cancelled?
- 1.0% of scheduled flights were cancelled (19 of 1,851).
- How long are typical delays?
- Across all flights the average arrival delay was 15 min (early arrivals count as zero). Flights that were late arrived 61 min behind schedule on average, and 6.0% of flights were an hour or more late.
- How long is taxi time at IAD?
- Flights on this route spent 20 min taxiing from the gate to takeoff on average.
Related routes
Return trip: SEA to IAD — 83% on time
More flights from Washington
Data: U.S. DOT Bureau of Transportation Statistics, Aug 2025 – Jul 2026 (12 months). Latest month published by BTS: July 2026. Route: IAD → SEA, nonstop flights by US airlines that report to the DOT. How we calculate this.