Route reliability record

DFW→SEA

Dallas-Fort Worth to Seattle

Flights: 5,232
Period: July 2025 to June 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 77.6%. The late ones land about an hour behind schedule. That rests on 5,232 flights, of which Delta Air Lines flew 712 at 78.9% on time.

Delta Air Lines is the most reliable of the three carriers covered here at 78.9% on time across 712 flights.

On time

69.5%

Arrivals under 15 minutes late, of 5,113 completed flights

Avg delay

64 min

Across delayed arrivals only, not all flights

Cancelled

2.12%

National rate is 1.81%

Best carrier

Delta

78.9% on time across 712 flights

These figures cover 5,232 flights between July 2025 and June 2026. Beyond the headline rate, 9.3% 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 78.9% of the time; American Airlines manages 65.0%. Sample sizes sit next to every figure, because a two-point gap across 2,736 flights means less than a ten-point one.

On-time performance by carrier on DFW to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	712	78.9%	88 min	1.69%	B
Alaska Airlines	1,756	72.7%	57 min	1.48%	C
Frontier Airlinesthin sample	28	67.9%	43 min	0.00%	C+
American Airlines	2,736	65.0%	64 min	2.67%	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 33 points, against 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am916 flights82.3%
8am–11am1,129 flights75.1%
11am–2pm569 flights74.3%
2pm–5pm980 flights69.3%
5pm–8pm946 flights62.3%
8pm–5am692 flights49.6%

Scale runs 40% to 90%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 49.6% on time, against 82.3% 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 1,129 flights scheduled in it.

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.

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

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. July was the busiest month here, with 506 flights.

Across the week, Tuesday is the strongest day at 72.5% on time and Sunday the weakest at 66.1%. 6 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 100,000 reported delay minutes.

Late-arriving aircraft
39%
Carrier
33%
National Airspace System
18%
Extreme weather
9%
Security
1%

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 100,000 reported delay minutes here, that single category outweighs weather by 4 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 split is drawn from 100,021 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 82.3% on time here.

Cancellations sit at 2.12% against a national 1.81%, which is ordinary. Diversions add another 0.15%.

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. 9.3% of arrivals land a full hour or more behind schedule, against 8.1% 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 77.6% on time across 5,233 flights, 8 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 8 points of difference.

The sample behind these figures is 5,232 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. 5,113 completed flights over 12 months sit behind that.

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 30.5% of the 5,232 flights in this analysis, against 22.4% 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 78.9% on time across 712 flights. American Airlines is at the other end on 65.0%, 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 82.3% on time. The 8pm–5am window is the weakest at 49.6%, 33 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.

Where to go next

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, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures