Carrier performance at one airport
DL→SEA
Delta Air Lines at Seattle-Tacoma International
- Departures
- 32,382
- Period
- September 2025 to August 2026
- Routes
- 25
- Rank here
- #3 of 10
Delta Air Lines at Seattle lands a B, 3 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 32,382 flights, of which Envoy Air flew 760 at 85.3% on time.
Measured against the airport rather than the country, Delta Air Lines runs about a point ahead of the 79.6% weighted average across all carriers at SEA. That is the comparison worth making: every operator here works the same runways, the same airspace and the same weather.
Key figures
On time
80.7%
31,888 completed departures
Avg delay
64 min
Across delayed flights only
Cancelled
1.11%
At SEA, this carrier only
Rank here
#3
Of 10 carriers clearing the floor at SEA
These figures cover 32,000 flights between September 2025 and August 2026. The median arrival is 6 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.
Against the competition
Every carrier at SEA, ranked
The choice of carrier is not cosmetic here. Envoy Air arrives on time 85.3% of the time; JetBlue Airways manages 53.6%. Sample sizes sit next to every figure, because a two-point gap across 413 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Envoy Air | 760 | 85.3% | 74 min | 0.00% | A+ |
| SkyWest Airlines | 28,580 | 84.9% | 60 min | 0.75% | B+ |
| Delta Air Lines (this page) | 32,382 | 80.7% | 64 min | 1.11% | B |
| United Airlines | 8,683 | 79.9% | 74 min | 0.75% | B+ |
| American Airlines | 6,768 | 79.7% | 97 min | 1.73% | B |
| Alaska Airlines | 76,970 | 78.5% | 47 min | 0.89% | B+ |
| Frontier Airlines | 1,397 | 75.8% | 89 min | 2.22% | B |
| Southwest Airlines | 8,194 | 68.2% | 50 min | 0.44% | C+ |
| Hawaiian Airlines | 612 | 65.8% | 93 min | 1.47% | C |
| JetBlue Airways | 413 | 53.6% | 101 min | 4.60% | F− |
JetBlue Airways cancels 4.6% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
Route by route
Where Delta Air Lines flies from SEA
Delta Air Lines operates 25 routes out of SEA with enough volume to report. Route records inside one carrier at one airport still spread widely, because a short shuttle and a transcontinental have very different exposure to a late inbound.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SEA to ATL · Atlanta | 2,402 | 84.2% | 84 min | 0.75% | B+ |
| SEA to SLC · Salt Lake City | 2,232 | 86.8% | 59 min | 0.49% | A+ |
| SEA to LAX · Los Angeles | 2,229 | 81.6% | 59 min | 0.58% | B+ |
| SEA to PHX · Phoenix | 1,768 | 80.9% | 67 min | 0.96% | B+ |
| SEA to LAS · Las Vegas | 1,748 | 81.3% | 54 min | 1.09% | B |
| SEA to MSP · Minneapolis | 1,745 | 89.0% | 78 min | 0.74% | A+ |
| SEA to SAN · San Diego | 1,710 | 81.1% | 51 min | 0.94% | B+ |
| SEA to ANC · Anchorage | 1,609 | 77.5% | 62 min | 0.62% | B+ |
| SEA to DTW · Detroit | 1,515 | 87.1% | 71 min | 0.86% | A+ |
| SEA to JFK · New York | 1,338 | 79.3% | 70 min | 3.21% | B− |
| SEA to BOS · Boston | 1,067 | 79.8% | 71 min | 1.69% | B |
| SEA to SFO · San Francisco | 985 | 60.5% | 54 min | 1.73% | D |
| SEA to AUS · Austin | 950 | 80.1% | 67 min | 1.05% | B |
| SEA to ORD · Chicago | 922 | 75.7% | 73 min | 1.30% | B |
| SEA to SNA · Santa Ana | 891 | 82.4% | 71 min | 1.01% | B |
| SEA to DEN · Denver | 869 | 72.9% | 57 min | 0.92% | C+ |
| SEA to HNL · Honolulu | 789 | 76.4% | 53 min | 0.38% | B+ |
| SEA to DFW · Dallas-Fort Worth | 720 | 76.6% | 75 min | 1.53% | B |
| SEA to MCO · Orlando | 719 | 79.7% | 58 min | 1.39% | B |
| SEA to BNA · Nashville | 516 | 83.0% | 61 min | 0.97% | B+ |
| SEA to FAI · Fairbanks | 474 | 77.1% | 69 min | 2.11% | B |
| SEA to KOA · Kailua-Kona | 365 | 76.1% | 47 min | 2.19% | B |
| SEA to OGG · Kahului | 365 | 86.0% | 40 min | 0.82% | A+ |
| SEA to LIH · Lihue | 365 | 74.7% | 69 min | 1.64% | C |
| SEA to MIA · Miami | 365 | 80.7% | 65 min | 1.37% | B |
Flight by flight
Delta Air Lines flight numbers from SEA
73 Delta Air Lines flight numbers leaving SEA flew their main route often enough to have a record of their own. Grouped by destination.
- DL 928to ANC 13:3072.6%
- DL 936to ANC 21:2073.0%
- DL 542to ATL 13:3079.3%
- DL 554to ATL 11:4077.4%
- DL 560to ATL 16:0584.6%
- DL 562to ATL 07:2582.4%
- DL 569to ATL 06:0094.8%
- DL 652to ATL 23:5989.0%
- DL 739to AUS 07:1589.2%
- DL 831to AUS 11:3578.7%
- DL 848to AUS 17:4573.5%
- DL 815to BNA 17:3580.1%
- DL 459to BOS 07:5088.1%
- DL 473to BOS 22:2583.5%
- DL 558to CVG 11:4589.5%
- DL 786to DCA 07:2091.0%
- DL 2851to DEN 19:4076.1%
- DL 803to DFW 09:1581.1%
- DL 870to DFW 17:5574.0%
- DL 533to DTW 15:1585.1%
- DL 810to DTW 23:1589.6%
- DL 812to DTW 06:0092.0%
- DL 1706to DTW 11:4380.8%
- DL 2186to FAI 21:4578.7%
- DL 338to FLL 11:5575.3%
- DL 351to HNL 08:2583.6%
- DL 419to HNL 16:0570.7%
- DL 541to IAD 15:2076.5%
- DL 415to JFK 13:4571.5%
- DL 429to JFK 07:1588.4%
- DL 452to JFK 22:4084.4%
- DL 340to KOA 14:3076.1%
- DL 2880to LAS 12:0080.1%
- DL 2905to LAS 10:1582.9%
- DL 2922to LAS 07:2091.1%
- DL 2949to LAS 20:2078.9%
- DL 1628to LAX 07:1590.6%
- DL 2769to LAX 10:1583.8%
- DL 2830to LAX 13:3083.8%
- DL 2854to LAX 19:5974.8%
- DL 2861to LAX 17:5974.2%
- DL 2914to LAX 12:4584.0%
- DL 345to LIH 14:3074.7%
- DL 2256to MCI 17:5077.4%
- DL 328to MCO 08:5074.8%
- DL 448to MCO 23:1584.7%
- DL 506to MIA 08:0080.7%
- DL 536to MSP 09:2590.6%
- DL 941to MSP 12:0088.9%
- DL 943to MSP 06:0096.4%
- DL 949to MSP 18:0581.5%
- DL 953to MSP 23:5990.9%
- DL 344to OGG 13:5986.0%
- DL 2055to ORD 07:1083.4%
- DL 2108to ORD 17:5573.0%
- DL 2442to PHX 13:3080.4%
- DL 2447to PHX 09:5578.9%
- DL 2449to PHX 11:5078.8%
- DL 2698to PHX 18:3073.7%
- DL 489to RDU 15:5576.3%
- DL 2508to SAN 07:1589.9%
- DL 2572to SAN 11:2581.6%
- DL 2613to SAN 15:2582.5%
- DL 2672to SAN 19:3574.1%
- DL 1412to SFO 10:2560.1%
- DL 2635to SFO 21:2069.6%
- DL 1016to SLC 09:2590.0%
- DL 1120to SLC 13:3083.0%
- DL 1128to SLC 05:3093.7%
- DL 1165to SLC 17:0080.4%
- DL 1239to SLC 19:5081.2%
- DL 1265to SLC 11:1585.1%
- DL 358to TPA 11:5578.7%
Departure window
Best time of day for this operation
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 12 points, against 32 points between the best and worst carrier.
- 5am–8am5,893 flights88.3%
- 8am–11am5,406 flights81.0%
- 11am–2pm6,442 flights79.4%
- 2pm–5pm5,066 flights77.5%
- 5pm–8pm4,260 flights76.6%
- 8pm–5am5,315 flights80.1%
Scale runs 70% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 88.3% of the time, against 76.6% for the evening window. That is 12 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 6,442 flights scheduled in it.
Across the year
Seasonal pattern
December is the weak month at 73.6% on time, against 85.7% 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 3,037 flights.
Delay causes
What holds this operation up
- 52%Carrier
- 23%National Airspace System
- 22%Late-arriving aircraft
- 3%Extreme weather
- 0%Security
The largest share of delay minutes, 52%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 206,000 of the 395,000 delay minutes reported here. The split is drawn from 394,546 reported delay minutes.
Cancellations sit at 1.11% against a national 1.89%, which is ordinary. Diversions add another 0.42%.
5.8% 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.
32,382 flights sit behind these numbers, which is a large enough sample that the headline rate is not moving on noise. Where a sub-group falls below 30 flights the site shows a dash instead of a percentage.
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 85.7% on time and December 73.6%, a swing of 12 points. If the dates move at all, move them out of December before you think about anything else. 31,888 completed flights over 12 months sit behind that.
Common questions
Delta Air Lines at SEA
How often is Delta Air Lines at SEA delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 19.3% of the 32,382 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on Delta Air Lines at SEA?
Envoy Air leads at 85.3% on time across 760 flights. JetBlue Airways is at the other end on 53.6%, a gap of 32 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 Delta Air Lines at SEA?
The 5am–8am departure window is the strongest at 88.3% on time. The 5pm–8pm window is the weakest at 76.6%, 12 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 Delta Air Lines at SEA?
December is the weakest month at 73.6% on time, compared with 85.7% in September. Across the year that is 12 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
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.