Carrier route record
ASIAD→SEA
Alaska Airlines · Washington to Seattle
- Flights
- 835
- Period
- September 2025 to August 2026
- Share of route
- 46%
- Carriers
- 3
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Alaska Airlines.
Alaska on IAD to SEA sits in the middle of the pack with a B. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.3%. The late ones land roughly 55 minutes behind schedule. That rests on 835 flights, with a median arrival 3 minutes early.
The US average over the same twelve months is 77.3%, so there is little to separate Alaska on IAD to SEA from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
75.4%
Arrivals under 15 minutes late, of 824 completed flights
Avg delay
53 min
Across delayed arrivals only, not all flights
Cancelled
1.20%
National rate is 1.89%
Whole route
77.7%
Every carrier on IAD to SEA, 1,821 flights
These figures cover 835 flights between September 2025 and August 2026. The median arrival is 3 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
Alaska against every carrier on IAD to SEA
Alaska flew 835 of the 1,821 flights on IAD to SEA, about 46% of it. Its 75.4% on time is 2 points worse than the route as a whole, which runs 77.7%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from United at 81.3% to Alaska at 75.4%. 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 | 625 | 81.3% | 66 min | 0.48% | B+ |
| Delta Air Linesthin sample | 361 | 76.6% | 88 min | 1.39% | B |
| Alaska Airlines (this page) | 835 | 75.4% | 53 min | 1.20% | B |
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Departure window
When Alaska runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 28 points, against half a point between the best and worst carrier.
- 5am–8am327 flights79.1%
- 8am–11am186 flights90.8%
- 11am–2pm—
- 2pm–5pm—
- 5pm–8pm322 flights62.5%
- 8pm–5am—
Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 62.5% on time, against 90.8% for the 8am–11am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5am–8am window is the busiest, with 327 flights scheduled in it.
Across the year
Alaska on IAD to SEA through the year
December is the weak month at 21.6% on time, against 92.2% in September. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. August was the busiest month here, with 93 flights.
Across the week, Thursday is the strongest day at 79.2% on time and Monday the weakest at 70.9%, a spread of 8 points.
Arrival by arrival
How late Alaska on IAD to SEA runs when it is late
Alaska on IAD to SEA often beats the schedule: 232 of 824 completed flights, 28%, arrived 15 minutes or more early. The 203 late arrivals split 81 under half an hour, 66 between 30 and 60 minutes, and 56 an hour or more.
- 15+ min early232 flights28.2%
- Within 15 min389 flights47.2%
- 15–29 min late81 flights9.8%
- 30–59 min late66 flights8.0%
- 1–2 hours late39 flights4.7%
- 2+ hours late17 flights2.1%
Scale runs 0% to 100%.
Share of 824 completed flights by arrival against schedule.
38 of 154 late departures made up the time and arrived on time, 25% of them. In the other direction, 87 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SEA.
The worst days
Worst days for Alaska on IAD to SEA
The latest arrival of the period was on 20 May 2026, 4 hours 49 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 20 May 2026 | 4 hours 49 minutes | Late-arriving aircraft |
| 26 January 2026 | 4 hours 46 minutes | Carrier |
| 7 August 2026 | 4 hours 39 minutes | Late-arriving aircraft |
| 27 April 2026 | 3 hours 30 minutes | Late-arriving aircraft |
| 14 June 2026 | 3 hours 23 minutes | Extreme weather |
Delay causes
Why Alaska runs late on this route
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 11,000 reported delay minutes.
- 36%National Airspace System
- 26%Late-arriving aircraft
- 24%Carrier
- 12%Extreme weather
- 2%Security
Extreme weather accounts for 12% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.0 times the usual weather exposure. The split is drawn from 10,692 reported delay minutes.
36% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 3,844 minutes out of 11,000, against a national NAS share of 21%.
Cancellations sit at 1.20% against a national 1.89%, which is ordinary. Diversions add another 0.12%.
Connections and stage length
What a delay here costs
6.8% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last roughly 55 minutes, 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 83.3% on time across 835 flights, 8 points above 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 8 points of difference.
One caution: this is a thin sample. 835 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 Alaska on IAD to SEA
Put together: treat all of this as provisional. 835 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 75.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 824 completed flights over 12 months sit behind that.
Related
Where to go next
- IAD to SEA, every carrier
- Alaska on SEA to IAD, the return leg
- United Airlines on IAD to SEA81.3%
- Delta Air Lines on IAD to SEA76.6%
- Alaska Airlines network-wide record
- Washington Dulles International (IAD) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- 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
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.