Route reliability record
DTW→SEA
Detroit to Seattle
- Flights
- 2,076
- Period
- July 2025 to June 2026
- Distance
- 1,927 mi
- Carriers
- 2
This route sits in the middle of the pack with a C+. Close to three flights in four arrive on time by the DOT's definition, 4 points worse than the national rate of 77.6%. The late ones land roughly 55 minutes behind schedule. That rests on 2,076 flights, of which Alaska Airlines flew 541 at 74.9% on time.
The national on-time rate over the same period is 77.6%, so this route runs 4 points behind the country as a whole. Across a thousand flights that is about 44 extra late arrivals.
Key figures
On time
73.2%
Arrivals under 15 minutes late, of 2,054 completed flights
Avg delay
54 min
Across delayed arrivals only, not all flights
Cancelled
0.87%
National rate is 1.81%
Best carrier
Alaska
74.9% on time across 541 flights
These figures cover 2,076 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
Which airline is most reliable on DTW to SEA
The two carriers here are closely matched: 2 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Alaska Airlines | 541 | 74.9% | 48 min | 0.37% | C+ |
| Delta Air Lines | 1,535 | 72.6% | 55 min | 1.04% | C |
No carrier stands out. Alaska tops the table at 74.9%, 2 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 25 points, against 2 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am260 flights81.4%
- 8am–11am366 flights77.7%
- 11am–2pm365 flights78.9%
- 2pm–5pm314 flights67.5%
- 5pm–8pm473 flights74.9%
- 8pm–5am298 flights56.6%
Scale runs 50% to 85%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 56.6% on time, against 81.4% 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 5pm–8pm window is the busiest, with 473 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 52 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
December is the weak month at 37.7% on time, against 89.8% 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 228 flights.
Across the week, Tuesday is the strongest day at 78.4% on time and Sunday the weakest at 68.1%. 10 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Carrier accounts for 44% of the 29,000 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.
- 44%Carrier
- 29%National Airspace System
- 24%Late-arriving aircraft
- 3%Extreme weather
- 0%Security
The largest share of delay minutes, 44%, 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 13,000 of the 29,000 delay minutes reported here. The split is drawn from 29,497 reported delay minutes.
Cancellations are rare at 0.87%, 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 actually 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 are the roughly 55 minutes kind, 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 84.7% on time across 2,072 flights, 12 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 12 points of difference.
The sample behind these figures is 2,076 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 this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 89.8% on time and December 37.7%, a swing of 52 points. If the dates move at all, move them out of December before you think about anything else. 2,054 completed flights over 12 months sit behind that.
Common questions
DTW to SEA questions
How often is DTW to SEA delayed?
About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 26.8% of the 2,076 flights in this analysis, against 22.4% nationally. Delayed flights are late by roughly 55 minutes on average.
Which airline is most reliable on DTW to SEA?
Alaska Airlines leads at 74.9% on time across 541 flights. Delta Air Lines is at the other end on 72.6%, a gap of 2 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on DTW to SEA?
The 5am–8am departure window is the strongest at 81.4% on time. The 8pm–5am window is the weakest at 56.6%, 25 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are December delays on DTW to SEA?
December is the weakest month at 37.7% on time, compared with 89.8% in September. Across the year that is 52 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SEA to DTW — the return legseparate record
- Detroit Metropolitan Wayne County (DTW) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Alaska Airlines on-time record74.9%
- Delta Air Lines on-time record72.6%
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. DTW to SEA and SEA to DTW are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.