Carrier route record

DLSEA→DTW

Delta Air Lines · Seattle to Detroit

Flights: 1,532
Period: July 2025 to June 2026
Share of route: 74%
Carriers: 2

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

Delta on SEA to DTW earns an A. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.6%. When something does go wrong the average delay runs about an hour. That rests on 1,532 flights, with a median arrival 8 minutes early.

Set against the rest of the country, Delta's SEA to DTW record is 8 points better than the US average of 77.6%. That gap is worth roughly 77 fewer late arrivals for every thousand flights.

On time

85.3%

Arrivals under 15 minutes late, of 1,511 completed flights

Avg delay

65 min

Across delayed arrivals only, not all flights

Cancelled

1.04%

National rate is 1.81%

Whole route

84.7%

Every carrier on SEA to DTW, 2,072 flights

These figures cover 1,532 flights between July 2025 and June 2026. The median arrival is 8 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

Delta against every carrier on SEA to DTW

Delta flew 1,532 of the 2,072 flights on SEA to DTW, most of the route. Its 85.3% on time is about level with the route as a whole at 84.7%. Ranked by on-time rate it is first 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 (this page)	1,532	85.3%	65 min	1.04%	A
Alaska Airlines	540	83.1%	46 min	0.19%	B+

Flight by flight

Delta flight numbers on SEA to DTW

Departure window

When Delta runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 12 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–8am365 flights90.5%
8am–11am211 flights87.9%
11am–2pm352 flights78.4%
2pm–5pm222 flights87.3%
5pm–8pm—
8pm–5am382 flights84.1%

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

The weak window here is the middle of the day, not the evening: 11am–2pm runs 78.4% on time against 90.5% for 5am–8am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 8pm–5am window is the busiest, with 382 flights scheduled in it.

Across the year

Delta on SEA to DTW through the year

Darker means more delays. Figures are on-time percentages.October best, August worst

August is the worst month at 74.8% on time, 20 points below October, the best at 94.3%. 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. July was the busiest month here, with 170 flights.

Across the week, Tuesday is the strongest day at 89.5% on time and Friday the weakest at 80.1%. 9 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Carrier accounts for 51% of the 14,000 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
51%
Late-arriving aircraft
32%
National Airspace System
14%
Extreme weather
3%

The largest share of delay minutes, 51%, 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 7,306 of the 14,000 delay minutes reported here. The split is drawn from 14,333 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 90.5% on time here.

Cancellations sit at 1.04% against a national 1.81%, which is ordinary. Diversions add another 0.33%.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 4.1% 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 72.6% on time across 1,535 flights, 13 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 13 points of difference.

The sample behind these figures is 1,532 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.

What to do with this

Booking Delta on SEA to DTW

Put together: the calendar is the biggest lever here, not the carrier or the hour. October runs 94.3% on time and August 74.8%, a swing of 20 points. If the dates move at all, move them out of August before you think about anything else. 1,511 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