Route reliability record
DTW→SEA
Detroit to Seattle
- Flights
- 2,067
- Period
- September 2025 to August 2026
- Distance
- 1,927 mi
- Carriers
- 2
This route 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 77.3%. The late ones land about an hour behind schedule. That rests on 2,067 DTW to SEA flights, of which Alaska Airlines flew 549 at 76.9% on time.
Best time to fly DTW to SEA: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 81.5% of the time and Tuesday flights 78.0%, against 72.8% for the route overall.
The national on-time rate over the same period is 77.3%, so this route runs 5 points behind the country as a whole. Across a thousand flights that is about 45 extra late arrivals.
Key figures
On time
72.8%
Arrivals under 15 minutes late, of 2,049 completed flights
Avg delay
56 min
Across delayed arrivals only, not all flights
Cancelled
0.68%
National rate is 1.89%
Best carrier
Alaska
76.9% on time across 549 flights
These figures cover 2,067 flights between September 2025 and August 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.
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Carrier by carrier
Which airline is most reliable on DTW to SEA
The two carriers here are closely matched: 6 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 | 549 | 76.9% | 52 min | 0.36% | B+ |
| Delta Air Lines | 1,518 | 71.3% | 57 min | 0.79% | C+ |
No carrier stands out. Alaska tops the table at 76.9%, 6 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on DTW to SEA
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Detroit to Seattle
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. DTW → SEADetroit to Seattle | Alaska Airlines | 76.6% | 76.9% | 0.36% | 5am–8am, Sat | AS 313 17:31 |
| 2. DTW → SEADetroit to Seattle | Delta Air Lines | 70.7% | 71.3% | 0.79% | 5am–8am, Tue | DL 728 12:20 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 22 points, against 6 points between the best and worst carrier.
- 5am–8am281 flights81.5%
- 8am–11am366 flights74.0%
- 11am–2pm365 flights76.8%
- 2pm–5pm271 flights67.9%
- 5pm–8pm482 flights74.7%
- 8pm–5am302 flights59.5%
Scale runs 50% to 85%.
The 8pm–5am window is where this operation falls apart: 59.5% on time, against 81.5% 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 482 flights scheduled in it.
Explore
Filter DTW to SEA by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On DTW to SEA, the best departure window is 5am–8am at 81.5% on time and the worst is 8pm–5am at 59.5%, a wide gap of 22.0 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am81.5%
- 8–11am74.0%
- 11am–2pm76.8%
- 2–5pm67.9%
- 5–8pm74.7%
- 8pm–5am59.5%
best all US flightsScale 50% to 95%.
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. August was the busiest month here, with 217 flights.
Across the week, Tuesday is the strongest day at 78.0% on time and Sunday the weakest at 66.3%, a spread of 12 points.
Delay causes
Why this route gets delayed
Carrier accounts for 50% of the 31,000 delay minutes carriers reported here, and the remaining four split what is left.
- 50%Carrier
- 27%National Airspace System
- 20%Late-arriving aircraft
- 2%Extreme weather
- 0%Security
The largest share of delay minutes, 50%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 16,000 of the 31,000 delay minutes reported here. The split is drawn from 31,248 reported delay minutes.
Cancellations are rare at 0.68%, below the national 1.89% 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
6.4% of arrivals land an hour or more late, close to the national 8.3%, so 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 86.6% on time across 2,063 flights, 14 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 14 points of difference.
The sample behind these figures is 2,067 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.
Work out the risk of missing a connection in SEA after this flight
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. 2,049 completed flights over 12 months sit behind that.
Common questions
DTW to SEA questions
How often is DTW to SEA delayed?
Roughly one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 27.2% of the 2,067 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on DTW to SEA?
Alaska Airlines leads at 76.9% on time across 549 flights. Delta Air Lines is at the other end on 71.3%, a gap of 6 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 81.5% on time. The 8pm–5am window is the weakest at 59.5%, 22 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 DTW to SEA76.9%
- Delta Air Lines on DTW to SEA71.3%
- DTW to ORD, a related route72.2%
- LAX to SEA, a related route85.0%
- DTW to ATL, a related route78.9%
- Alaska Airlines on-time record76.9%
- Delta Air Lines on-time record71.3%
- The best time of day to fly, according to 7.05 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.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.