Carrier route record

ASBOI→SEA

Alaska Airlines · Boise to Seattle

Flights: 891
Period: July 2025 to June 2026
Share of route: 23%
Carriers: 2

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

Alaska on BOI to SEA earns a B+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 6 points better than the national rate of 77.6%. When something does go wrong the average delay runs about 50 minutes. That rests on 891 flights, with a median arrival 7 minutes early.

Set against the rest of the country, Alaska's BOI to SEA record is 6 points better than the US average of 77.6%. That gap is worth roughly 64 fewer late arrivals for every thousand flights.

On time

84.0%

Arrivals under 15 minutes late, of 884 completed flights

Avg delay

50 min

Across delayed arrivals only, not all flights

Cancelled

0.79%

National rate is 1.81%

Whole route

85.7%

Every carrier on BOI to SEA, 3,820 flights

These figures cover 891 flights between July 2025 and June 2026. The median arrival is 7 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.

Carrier by carrier

Alaska against every carrier on BOI to SEA

Alaska flew 891 of the 3,820 flights on BOI to SEA, about 23% of it. Its 84.0% on time is 2 points worse than the route as a whole, which runs 85.7%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from SkyWest at 86.2% to Alaska at 84.0%.

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.

On-time performance by carrier on BOI to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlines	2,929	86.2%	58 min	0.27%	A+
Alaska Airlines (this page)	891	84.0%	50 min	0.79%	B+

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 15 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am362 flights91.6%
8am–11am—
11am–2pm28 flights—
2pm–5pm147 flights81.5%
5pm–8pm353 flights76.4%
8pm–5am1 flights—

Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 91.6% of the time, against 76.4% for the evening window. That is 15 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 362 flights scheduled in it.

Across the year

Alaska on BOI to SEA through the year

Darker means more delays. Figures are on-time percentages.March best, November worst

Delays peak in November, when the on-time rate falls to 71.9%. March is the strongest month at 93.8%. Moving a flexible trip across that boundary buys 22 points. March was the busiest month here, with 97 flights.

Across the week, Sunday is the strongest day at 88.4% on time and Thursday the weakest at 74.0%. 14 points is a smaller lever than departure hour, but it is free.

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 6,991 reported delay minutes.

Carrier
39%
National Airspace System
32%
Late-arriving aircraft
28%
Extreme weather
1%

The largest share of delay minutes, 39%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 2,704 of the 6,991 delay minutes reported here. The split is drawn from 6,991 reported delay minutes.

32% 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 2,262 minutes out of 6,991, against a national NAS share of 21%.

Cancellations are rare at 0.79%, 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 stage length

What a delay here costs

Badly late arrivals are rare here: only 3.6% 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 399 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.

The return leg is a different operation and performs like one: it runs 80.8% on time across 891 flights, 3 points below 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 3 points of difference.

One caution: this is a thin sample. 891 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 BOI to SEA

Put together: treat all of this as provisional. 891 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 84.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 884 completed flights over 12 months sit behind that.

Where to go next

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