Route reliability record
DFW→SEA
Dallas-Fort Worth to Seattle
- Flights
- 5,238
- Period
- June 2025 to May 2026
- Distance
- 1,660 mi
- Carriers
- 4
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, 8 points worse than the national rate of 77.4%. The late ones land about an hour behind schedule. That rests on 5,238 flights, of which Delta Air Lines flew 710 at 79.5% on time.
Delta Air Lines is the most reliable of the three carriers covered here at 79.5% on time across 710 flights.
Key figures
On time
69.4%
Arrivals under 15 minutes late, of 5,116 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
2.20%
National rate is 1.80%
Best carrier
Delta
79.5% on time across 710 flights
These figures cover 5,238 flights between June 2025 and May 2026. Beyond the headline rate, 9.1% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Which airline is most reliable on DFW to SEA
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 79.5% of the time; American Airlines manages 65.9%. Sample sizes sit next to every figure, because a two-point gap across 2,735 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 710 | 79.5% | 87 min | 1.69% | B |
| Frontier Airlinesthin sample | 37 | 73.0% | 43 min | 0.00% | C+ |
| Alaska Airlines | 1,756 | 70.8% | 57 min | 1.48% | C |
| American Airlines | 2,735 | 65.9% | 62 min | 2.82% | C |
The spread between Delta and American is 14 points, wide enough that it should decide the booking. On a hundred trips that is 14 more arrivals inside the on-time window.
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 34 points, against 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am925 flights82.8%
- 8am–11am1,129 flights74.7%
- 11am–2pm569 flights72.6%
- 2pm–5pm975 flights69.5%
- 5pm–8pm977 flights62.4%
- 8pm–5am663 flights49.2%
Scale runs 40% to 90%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 49.2% on time, against 82.8% 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.
Across the year
When delays peak on this route
This route's year swings by 17 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 60.8% on time, against 77.7% in February. 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.
Across the week, Tuesday is the strongest day at 72.4% on time and Sunday the weakest at 67.3%. 5 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 98,000 reported delay minutes.
- 39%Late-arriving aircraft
- 34%Carrier
- 19%National Airspace System
- 8%Extreme weather
- 1%Security
39% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 98,000 reported delay minutes here, that single category outweighs weather by 5 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit.
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 82.8% on time here.
Cancellations sit at 2.20% against a national 1.80%, which is ordinary. Diversions add another 0.13%.
Connections and stage length
What a delay here actually costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.1% of arrivals land a full hour or more behind schedule, against 8.2% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
At 1,660 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 76.7% on time across 5,237 flights, 7 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 7 points of difference.
The sample behind these figures is 5,238 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. February runs 77.7% on time and December 60.8%, a swing of 17 points. If the dates move at all, move them out of December before you think about anything else.
Common questions
DFW to SEA questions
How often is DFW to SEA delayed?
Roughly one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 30.6% of the 5,238 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on DFW to SEA?
Delta Air Lines leads at 79.5% on time across 710 flights. American Airlines is at the other end on 65.9%, a gap of 14 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 DFW to SEA?
The 5am–8am departure window is the strongest at 82.8% on time. The 8pm–5am window is the weakest at 49.2%, 34 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 DFW to SEA?
December is the weakest month at 60.8% on time, compared with 77.7% in February. Across the year that is 17 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 DFW — the return legseparate record
- Dallas/Fort Worth International (DFW) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on-time record79.5%
- Frontier Airlines on-time record73.0%
- Alaska Airlines on-time record70.8%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. DFW to SEA and SEA to DFW 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, June 2025 to May 2026. Updated monthly. How this data is collected.