Airport month record
SEAAUG
Seattle-Tacoma International in August 2026
- Departures
- 15,908
- Month
- August 2026
- National, same month
- 73.1%
- Carriers
- 9
Historical statistics for August 2026, not live status or a forecast for this year’s August. For today’s conditions at SEA, see live FAA status.
SEA in August sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, level with the national rate of 73.1%. The late ones land about 55 minutes behind schedule. That rests on 15,908 flights, of which Delta Air Lines flew 2,977 at 78.0% on time.
Delta Air Lines is the most reliable of the six carriers covered here at 78.0% on time across 2,977 flights.
Key figures
On time
72.6%
Arrivals under 15 minutes late, of 15,720 completed departures
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.65%
Nationally in August: 1.86%
Whole year
79.5%
SEA across all twelve months
These figures cover 15,908 departures from Seattle-Tacoma International in August 2026. On time means an arrival less than 15 minutes after the scheduled gate time, the DOT's threshold, and the national comparison uses every US departure in the same month rather than the whole year.
Against the year
August next to SEA's other months
Against SEA's own year, August ran 7 points worse than the twelve-month rate of 79.5%, which makes it number eleven of twelve months, best first.
| Month | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| September 2025 | 14,552 | 82.9% | 50 min | 0.29% | B+ |
| October 2025 | 13,859 | 82.9% | 58 min | 1.16% | B |
| November 2025 | 12,616 | 81.9% | 58 min | 1.69% | B |
| December 2025 | 13,023 | 74.0% | 59 min | 1.02% | C |
| January 2026 | 11,927 | 81.6% | 60 min | 1.91% | B |
| February 2026 | 11,000 | 84.4% | 56 min | 0.78% | B+ |
| March 2026 | 12,830 | 80.2% | 64 min | 2.23% | B |
| April 2026 | 12,864 | 85.6% | 56 min | 0.17% | A+ |
| May 2026 | 14,564 | 82.2% | 52 min | 0.41% | B+ |
| June 2026 | 15,402 | 78.1% | 57 min | 0.48% | B+ |
| July 2026 | 16,214 | 71.8% | 57 min | 0.76% | C+ |
| August 2026 (this page) | 15,908 | 72.6% | 55 min | 0.65% | C+ |
Departure window
The best time of day to leave SEA in August
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 24 points, against 25 points between the best and worst carrier.
- 5am–8am1,874 flights88.6%
- 8am–11am3,353 flights77.6%
- 11am–2pm3,022 flights67.5%
- 2pm–5pm2,343 flights64.2%
- 5pm–8pm2,234 flights68.2%
- 8pm–5am3,082 flights72.0%
Scale runs 55% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 88.6% of the time, against 64.2% for the afternoon window. That is 24 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 3,353 flights scheduled in it.
Across the week, Tuesday is the strongest day at 80.8% on time and Monday the weakest at 64.2%, a spread of 17 points.
Carrier by carrier
Which airlines ran best at SEA in August
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 78.0% of the time; Southwest Airlines manages 53.3%. Sample sizes sit next to every figure, because a two-point gap across 994 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Alaska Airlines | 7,449 | 71.3% | 47 min | 0.91% | C+ |
| Delta Air Lines | 2,977 | 78.0% | 58 min | 0.50% | B+ |
| SkyWest Airlines | 2,567 | 77.8% | 53 min | 0.04% | B+ |
| Southwest Airlines | 994 | 53.3% | 60 min | 0.30% | F+ |
| United Airlines | 907 | 73.3% | 62 min | 0.55% | C+ |
| American Airlines | 692 | 74.4% | 89 min | 0.29% | C+ |
| Frontier Airlinesthin sample | 155 | 72.8% | 117 min | 1.94% | C |
| JetBlue Airwaysthin sample | 93 | 30.2% | 106 min | 7.53% | F− |
| Envoy Airthin sample | 74 | 84.7% | 62 min | 0.00% | B+ |
The spread between Delta and Southwest is 25 points, wide enough that it should decide the booking. On a hundred trips that is 25 more arrivals inside the on-time window.
Route by route
Busiest routes out of SEA in August
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SEA to LAX · Los Angeles | 717 | 73.4% | 51 min | 0.14% | C+ |
| SEA to ANC · Anchorage | 686 | 75.0% | 41 min | 0.29% | B+ |
| SEA to DEN · Denver | 652 | 63.8% | 73 min | 0.15% | D+ |
| SEA to SFO · San Francisco | 645 | 48.6% | 47 min | 0.78% | F+ |
| SEA to ORD · Chicago | 586 | 71.0% | 73 min | 0.51% | C+ |
| SEA to PHX · Phoenix | 565 | 68.8% | 52 min | 0.71% | C+ |
| SEA to LAS · Las Vegas | 486 | 68.8% | 59 min | 1.03% | C |
| SEA to SAN · San Diego | 478 | 60.6% | 46 min | 0.63% | D+ |
| SEA to DFW · Dallas-Fort Worth | 475 | 70.5% | 64 min | 0.21% | C+ |
| SEA to SJC · San Jose | 436 | 67.2% | 52 min | 0.69% | C+ |
| SEA to SMF · Sacramento | 433 | 78.4% | 52 min | 0.46% | B+ |
| SEA to PDX · Portland | 430 | 71.7% | 43 min | 0.70% | C+ |
| SEA to GEG · Spokane | 407 | 72.2% | 61 min | 0.00% | C+ |
| SEA to SLC · Salt Lake City | 382 | 75.3% | 42 min | 0.26% | B+ |
| SEA to SNA · Santa Anathin sample | 346 | 80.9% | 35 min | 1.16% | B |
| SEA to ATL · Atlantathin sample | 333 | 84.1% | 62 min | 1.50% | B |
| SEA to BOS · Bostonthin sample | 322 | 66.8% | 68 min | 1.55% | C |
| SEA to BOI · Boisethin sample | 318 | 85.4% | 42 min | 0.31% | A+ |
| SEA to MSP · Minneapolisthin sample | 283 | 84.8% | 90 min | 0.00% | B+ |
| SEA to JFK · New Yorkthin sample | 278 | 71.2% | 96 min | 3.60% | C− |
| SEA to ONT · Ontariothin sample | 249 | 77.0% | 53 min | 0.40% | B+ |
| SEA to HNL · Honoluluthin sample | 242 | 62.4% | 60 min | 2.89% | D |
| SEA to EWR · Newarkthin sample | 229 | 79.3% | 68 min | 2.62% | B |
| SEA to OAK · Oaklandthin sample | 218 | 62.3% | 53 min | 1.38% | D |
| SEA to AUS · Austinthin sample | 217 | 68.7% | 51 min | 0.00% | C+ |
Delay causes
What held SEA up in August
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 235,000 reported delay minutes.
- 39%Carrier
- 35%Late-arriving aircraft
- 24%National Airspace System
- 2%Extreme weather
- 0%Security
35% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 235,000 reported delay minutes here, that single category outweighs weather by 17 to one. The split is drawn from 235,298 reported delay minutes.
Cancellations are rare at 0.65%, below the national 1.86% 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.
6.9% of arrivals land an hour or more late, close to the national 10.9%, 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 55 minutes, which a normal layover absorbs.
What to do with this
Flying from SEA in August
For a August trip through SEA: plan on this being one of the airport's harder months. The 5am–8am departures held up best at 88.6% on time, and with 6.9% of arrivals an hour or more late, a connection here deserves more slack than the same trip in April would.
Related
Where to go next
- Seattle-Tacoma International (SEA), the whole year
- SEA in September82.9%
- SEA in October82.9%
- SEA in November81.9%
- SEA in December74.0%
- SEA in January81.6%
- SEA in February84.4%
- SEA in March80.2%
- SEA in April85.6%
- SEA in May82.2%
- SEA in June78.1%
- SEA in July71.8%
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.