Flight number record

AS 351

Alaska Airlines · Washington to Seattle

Route: IAD → SEA
Departs: 07:00
Flights: 306
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s AS 351, check with Alaska Airlines.

AS 351 lands a B+, 2 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by roughly 50 minutes on average. That is a workable record, not a spotless one. That rests on 306 flights, with a median arrival 9 minutes early.

On time

79.9%

Arrivals under 15 minutes late, of 304 completed flights

Avg delay

48 min

Across delayed arrivals only, not all flights

Cancelled

0.65%

National rate is 1.81%

1 hour+ late

4.9%

National rate is 8.1%

These figures cover 306 flights between July 2025 and June 2026. The median arrival is 9 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.

Schedule

When AS 351 flies

AS 351 flies IAD to SEA without a single fixed slot. Its most common scheduled departure was 07:00, used on 80 of 306 flights, with 06:30 (50 flights) and 07:05 (33 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 07:0080 flights26.1%
Departs 06:3050 flights16.3%
Departs 07:0533 flights10.8%

Scale runs 0% to 100%. Rows with fewer than 30 flights show a dash.

Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.

A 07:00 departure sits in the 5am–8am window. Across every US flight scheduled in that window the on-time rate is 89.3%, and AS 351 runs 9 points worse at 79.9%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

Against the route

AS 351 next to IAD to SEA

Every carrier on IAD to SEA combined arrived on time 76.6% of the time across 1,884 flights, so AS 351 is 3 points ahead of it. Alaska flew 835 flights on the same city pair under all its flight numbers, including this one, and those ran 73.7% on time. Across its whole network Alaska Airlines managed 79.1%, close to this flight's figure.

AS 351 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
AS 351thin sample	306	79.9%	48 min	0.65%	B+
All Alaska Airlines on IAD–SEA	835	73.7%	53 min	1.20%	C
All carriers on IAD–SEA	1,884	76.6%	63 min	1.01%	B
Alaska Airlines, whole network	293,372	79.1%	52 min	1.28%	B

Across the year

AS 351 quarter by quarter

AS 351 did not run the same all year. Its best quarter was Jul–Sep 2025 at 96.7% on time and its weakest Oct–Dec 2025 at 59.6%, a swing of 37 points on roughly 77 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Jul–Sep 202592 flights96.7%
Oct–Dec 202591 flights59.6%
Jan–Mar 202653 flights67.9%
Apr–Jun 202670 flights92.9%

Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.

By weekday, AS 351 ranged from 77.8% on Tuesday to 83.7% on Wednesday. With about 44 flights behind each day, a spread of 6 points is inside normal variation, so the day you fly is not worth changing for this flight.

Delay causes

Why AS 351 runs late

One category carries most of the weight here. National Airspace System accounts for 50% of the 2,930 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.

National Airspace System
50%
Late-arriving aircraft
23%
Carrier
18%
Extreme weather
8%
Security
1%

50% 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 1,456 minutes out of 2,930, against a national NAS share of 21%. The split is drawn from 2,930 delay minutes reported on AS 351.

Cancellations are rare at 0.65%, 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 routes

What a delay on this flight costs

Badly late arrivals are rare here: only 4.9% land an hour or more behind schedule, against 8.1% 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 same number turns up on one other city pair in the data, including FAI to ANC (36), but none flew often enough under AS 351 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to IAD to SEA only.

One caution: this is a thin sample. 306 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 AS 351

For a booking, read AS 351 as 79.9% on time with 0.65% cancelled over 306 flights. Those are rates from the past twelve months, not a forecast for any particular day.

Where to go next

A flight number here means Alaska Airlines’s own number as it reports to the DOT. How the figures are computed is on the methodology page.

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.

Key figures