Flight number record

AS 306

Alaska Airlines · Seattle to Boston

Route: SEA → BOS
Departs: 08:21
Flights: 365
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s AS 306, check with Alaska Airlines.

AS 306 sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.6%. The late ones land roughly 50 minutes behind schedule. That rests on 365 flights, with a median arrival right on schedule.

On time

74.2%

Arrivals under 15 minutes late, of 360 completed flights

Avg delay

52 min

Across delayed arrivals only, not all flights

Cancelled

1.37%

National rate is 1.81%

1 hour+ late

6.4%

National rate is 8.1%

These figures cover 365 flights between July 2025 and June 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.

Schedule

When AS 306 flies

AS 306 flies SEA to BOS without a single fixed slot. Its most common scheduled departure was 08:21, used on 50 of 365 flights, with 08:00 (45 flights) and 09:00 (42 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 08:2150 flights13.7%
Departs 08:0045 flights12.3%
Departs 09:0042 flights11.5%

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 08:21 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 84.1%, and AS 306 runs 10 points worse at 74.2%. 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 306 next to SEA to BOS

Every carrier on SEA to BOS combined arrived on time 74.5% of the time across 2,459 flights, so AS 306 is about level with it. Alaska flew 1,207 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%, which this flight trails by 5 points.

AS 306 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
AS 306	365	74.2%	52 min	1.37%	C
All Alaska Airlines on SEA–BOS	1,207	73.7%	48 min	0.99%	C+
All carriers on SEA–BOS	2,459	74.5%	68 min	1.14%	C
Alaska Airlines, whole network	293,372	79.1%	52 min	1.28%	B

Across the year

AS 306 quarter by quarter

AS 306 did not run the same all year. Its best quarter was Jan–Mar 2026 at 91.9% on time and its weakest Jul–Sep 2025 at 62.0%, a swing of 30 points on roughly 91 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 flights62.0%
Oct–Dec 202592 flights73.6%
Jan–Mar 202690 flights91.9%
Apr–Jun 202691 flights70.3%

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

By weekday, AS 306 did best on Monday at 82.0% on time and worst on Friday at 67.3%. Each day rests on about 52 flights, so a gap of 15 points is worth noticing but could still narrow in another year.

Delay causes

Why AS 306 runs late

One category carries most of the weight here. National Airspace System accounts for 66% of the 4,861 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
66%
Extreme weather
14%
Carrier
13%
Late-arriving aircraft
7%

Extreme weather accounts for 14% 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 quarterly figures above are the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.3 times the usual weather exposure. The split is drawn from 4,861 delay minutes reported on AS 306.

Cancellations sit at 1.37% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

Connections and routes

What a delay on this flight costs

6.4% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last roughly 50 minutes, which a normal layover absorbs.

At 2,496 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 BOS to SEA (116), but none flew often enough under AS 306 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to SEA to BOS only.

One caution: this is a thin sample. 365 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 306

For a booking, read AS 306 as 74.2% on time with 1.37% cancelled over 365 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