Carrier route record

DLDTW→SEA

Delta Air Lines · Detroit to Seattle

Flights: 1,535
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 DTW to SEA sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 1,535 flights, with a median arrival 2 minutes early.

The national on-time rate over the same period is 77.6%, so Delta on DTW to SEA runs 5 points behind the country as a whole. Across a thousand flights that is about 50 extra late arrivals.

On time

72.6%

Arrivals under 15 minutes late, of 1,516 completed flights

Avg delay

55 min

Across delayed arrivals only, not all flights

Cancelled

1.04%

National rate is 1.81%

Whole route

73.2%

Every carrier on DTW to SEA, 2,076 flights

These figures cover 1,535 flights between July 2025 and June 2026. The median arrival is 2 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 DTW to SEA

Delta flew 1,535 of the 2,076 flights on DTW to SEA, most of the route. Its 72.6% on time is about level with the route as a whole at 73.2%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from Alaska at 74.9% to Delta at 72.6%.

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 DTW to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlines	541	74.9%	48 min	0.37%	C+
Delta Air Lines (this page)	1,535	72.6%	55 min	1.04%	C

Flight by flight

Delta flight numbers on DTW to SEA

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 37 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–8am65 flights93.8%
8am–11am366 flights77.7%
11am–2pm364 flights78.9%
2pm–5pm271 flights68.3%
5pm–8pm171 flights74.7%
8pm–5am298 flights56.6%

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

The 8pm–5am window is where this operation falls apart: 56.6% on time, against 93.8% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 8am–11am window is the busiest, with 366 flights scheduled in it.

Across the year

Delta on DTW to SEA through the year

Darker means more delays. Figures are on-time percentages.September best, December worst

December is the weak month at 38.5% on time, against 90.8% in September. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 170 flights.

Across the week, Tuesday is the strongest day at 78.2% on time and Friday the weakest at 67.6%. 11 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 23,000 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%
National Airspace System
30%
Late-arriving aircraft
17%
Extreme weather
2%

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 12,000 of the 23,000 delay minutes reported here. The split is drawn from 23,038 reported delay minutes.

Cancellations sit at 1.04% against a national 1.81%, which is ordinary. Diversions add another 0.20%.

Connections and stage length

What a delay here costs

6.1% 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 about an hour, which a normal layover absorbs.

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 85.3% on time across 1,532 flights, 13 points above 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 1,535 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 DTW to SEA

Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 90.8% on time and December 38.5%, a swing of 52 points. If the dates move at all, move them out of December before you think about anything else. 1,516 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