Carrier route record

ASSEA→DTW

Alaska Airlines · Seattle to Detroit

Flights: 540
Period: July 2025 to June 2026
Share of route: 26%
Carriers: 2

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

Alaska on SEA to DTW lands a B+, 6 points better than the national rate of 77.6%. About one flight in six arrives 15 minutes late or worse, and those flights are late by roughly 45 minutes on average. That is a workable record, not a spotless one. That rests on 540 flights, with a median arrival 7 minutes early.

Set against the rest of the country, Alaska's SEA to DTW record is 6 points better than the US average of 77.6%. That gap is worth roughly 55 fewer late arrivals for every thousand flights.

On time

83.1%

Arrivals under 15 minutes late, of 533 completed flights

Avg delay

46 min

Across delayed arrivals only, not all flights

Cancelled

0.19%

National rate is 1.81%

Whole route

84.7%

Every carrier on SEA to DTW, 2,072 flights

These figures cover 540 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 SEA to DTW

Alaska flew 540 of the 2,072 flights on SEA to DTW, about 26% of it. Its 83.1% on time is 2 points worse than the route as a whole, which runs 84.7%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from Delta at 85.3% to Alaska at 83.1%.

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 SEA to DTW
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	1,532	85.3%	65 min	1.04%	A
Alaska Airlines (this page)	540	83.1%	46 min	0.19%	B+

Flight by flight

Alaska flight numbers on SEA to DTW

AS 31308:3085.0% · 362 flights

Departure window

When Alaska runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 540 flights.

5am–8am—
8am–11am362 flights85.0%
11am–2pm—
2pm–5pm—
5pm–8pm—
8pm–5am178 flights79.3%

Scale runs 70% to 90%. Rows with fewer than 30 flights show a dash.

The early departures do better, though not dramatically: 85.0% on time for the 8am–11am window against 79.3% for 8pm–5am. Worth taking if the schedule allows, not worth an extra connection. The 8am–11am window is the busiest, with 362 flights scheduled in it.

Across the year

Alaska on SEA to DTW through the year

Darker means more delays. Figures are on-time percentages.April best, July worst

July is the worst month at 72.7% on time, 22 points below April, the best at 95.0%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. May was the busiest month here, with 62 flights.

Across the week, Tuesday is the strongest day at 90.2% on time and Sunday the weakest at 76.6%. 14 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Alaska runs late on this route

One category carries most of the weight here. Carrier accounts for 48% of the 4,174 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.

Carrier
48%
Late-arriving aircraft
33%
National Airspace System
18%
Extreme weather
0%
Security
0%

The largest share of delay minutes, 48%, 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 2,024 of the 4,174 delay minutes reported here. The split is drawn from 4,174 reported delay minutes.

The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 85.0% on time here.

Cancellations are rare at 0.19%, 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 3.8% 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 1,927 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 74.9% on time across 541 flights, 8 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 8 points of difference.

One caution: this is a thin sample. 540 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 SEA to DTW

Put together: treat all of this as provisional. 540 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 83.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 533 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