Seattle, WA · departure reliability
SEA
Seattle-Tacoma International
- Departures
- 165,184
- Period
- July 2025 to June 2026
- Carriers
- 10
- US rank
- #9 by volume
Seattle
Seattle-Tacoma International lands a B+, 2 points better than the national rate of 77.6%. About one flight in five arrive 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 165,184 flights, of which Envoy Air flew 691 at 86.9% on time.
Envoy Air is the most reliable of the ten carriers covered here at 86.9% on time across 691 flights.
Key figures
On time
79.4%
Departures arriving under 15 minutes late at their destination
Avg delay
56 min
Across delayed flights only
Cancelled
0.99%
National rate is 1.81%
Best carrier
Envoy
86.9% on time here
These figures cover 165,000 flights between July 2025 and June 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.
Carrier by carrier
Which airlines run best out of SEA
The choice of carrier is not cosmetic here. Envoy Air arrives on time 86.9% of the time; JetBlue Airways manages 59.6%. 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 |
|---|---|---|---|---|---|
| Alaska Airlines | 76,697 | 77.2% | 47 min | 1.05% | B |
| Delta Air Lines | 32,257 | 81.5% | 65 min | 1.05% | B |
| SkyWest Airlines | 29,109 | 86.1% | 58 min | 0.71% | A+ |
| United Airlines | 8,804 | 80.2% | 76 min | 0.80% | B+ |
| Southwest Airlines | 8,105 | 70.0% | 48 min | 0.41% | C+ |
| American Airlines | 6,630 | 79.2% | 97 min | 2.07% | B |
| Frontier Airlines | 1,401 | 73.6% | 90 min | 2.28% | C |
| Hawaiian Airlines | 1,034 | 60.5% | 82 min | 1.26% | D |
| Envoy Air | 691 | 86.9% | 71 min | 0.00% | A+ |
| JetBlue Airways | 413 | 59.6% | 109 min | 0.73% | D+ |
The spread between Envoy and JetBlue is 27 points, wide enough that it should decide the booking. On a hundred trips that is 27 more arrivals inside the on-time window.
Route by route
Busiest routes out of SEA
Route-level records vary far more than the airport average. These are the 25 busiest departures from SEA, each with its own on-time rate against the airport-wide 79.4%.
| Route | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SEA to LAX · Los Angeles | 7,428 | 83.4% | 59 min | 0.92% | B+ |
| SEA to PHX · Phoenix | 7,268 | 79.2% | 56 min | 0.70% | B+ |
| SEA to SFO · San Francisco | 6,764 | 65.6% | 59 min | 1.20% | C |
| SEA to ANC · Anchorage | 6,681 | 75.2% | 51 min | 1.00% | B |
| SEA to DEN · Denver | 6,317 | 77.8% | 58 min | 0.85% | B+ |
| SEA to LAS · Las Vegas | 5,650 | 77.7% | 54 min | 0.83% | B+ |
| SEA to ORD · Chicago | 5,566 | 75.0% | 74 min | 1.28% | B |
| SEA to DFW · Dallas-Fort Worth | 5,233 | 77.6% | 79 min | 2.04% | B |
| SEA to GEG · Spokane | 5,221 | 82.5% | 51 min | 1.00% | B |
| SEA to PDX · Portland | 4,778 | 83.1% | 51 min | 0.67% | B+ |
| SEA to SAN · San Diego | 4,584 | 77.3% | 46 min | 1.22% | B |
| SEA to SMF · Sacramento | 4,407 | 81.9% | 50 min | 0.41% | B+ |
| SEA to SJC · San Jose | 4,371 | 81.6% | 48 min | 0.80% | B+ |
| SEA to SLC · Salt Lake City | 4,107 | 83.6% | 50 min | 0.93% | B+ |
| SEA to BOI · Boise | 3,972 | 85.8% | 49 min | 0.25% | A+ |
| SEA to SNA · Santa Ana | 3,967 | 85.1% | 49 min | 1.01% | A |
| SEA to ATL · Atlanta | 3,276 | 82.8% | 73 min | 0.55% | B+ |
| SEA to HNL · Honolulu | 2,938 | 65.5% | 71 min | 0.99% | C+ |
| SEA to JFK · New York | 2,906 | 75.3% | 62 min | 2.41% | B |
| SEA to MSP · Minneapolis | 2,689 | 85.5% | 55 min | 0.89% | A+ |
| SEA to ONT · Ontario | 2,550 | 82.9% | 50 min | 1.25% | B |
| SEA to BOS · Boston | 2,459 | 74.5% | 68 min | 1.14% | C |
| SEA to FAI · Fairbanks | 2,321 | 77.8% | 50 min | 1.03% | B |
| SEA to EWR · Newark | 2,235 | 81.2% | 69 min | 1.74% | B |
| SEA to IAH · Houston | 2,095 | 80.3% | 56 min | 0.62% | B+ |
Departure window
The best time of day to leave SEA
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 14 points, against 27 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am19,102 flights89.2%
- 8am–11am35,190 flights82.3%
- 11am–2pm31,872 flights76.2%
- 2pm–5pm23,932 flights77.1%
- 5pm–8pm23,972 flights75.0%
- 8pm–5am31,116 flights78.3%
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 89.2% of the time, against 75.0% for the evening window. That is 14 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 35,190 flights scheduled in it.
Across the year
When SEA runs late
SEA's year swings by 16 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.
July is the worst month at 69.2% on time, 16 points below April, the best at 85.6%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. July was the busiest month here, with 16,577 flights.
Across the week, Tuesday is the strongest day at 82.7% on time and Friday the weakest at 76.6%. 6 points is a smaller lever than departure hour, but it is free.
Delay causes
Why SEA gets delayed
One category carries most of the weight here. Carrier accounts for 43% of the 1.89 million delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 43%Carrier
- 30%Late-arriving aircraft
- 22%National Airspace System
- 5%Extreme weather
- 0%Security
The largest share of delay minutes, 43%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 812,000 of the 1.89 million delay minutes reported here. The split is drawn from 1,892,509 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 89.2% on time here.
Cancellations sit at 0.99% against a national 1.81%, which is ordinary. Diversions add another 0.33%.
5.3% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route are the about an hour kind, which a normal layover absorbs.
165,184 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.
What to do with this
Flying out of SEA
Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 85.6% on time and July 69.2%, a swing of 16 points. If the dates move at all, move them out of July before you think about anything else. 163,001 completed flights over 12 months sit behind that.
Common questions
SEA delay questions
How often is Seattle (SEA) delayed?
About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 20.6% of the 165,184 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on Seattle (SEA)?
Envoy Air leads at 86.9% on time across 691 flights. JetBlue Airways is at the other end on 59.6%, a gap of 27 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 Seattle (SEA)?
The 5am–8am departure window is the strongest at 89.2% on time. The 5pm–8pm window is the weakest at 75.0%, 14 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 July delays on Seattle (SEA)?
July is the weakest month at 69.2% on time, compared with 85.6% in April. Across the year that is 16 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 LAX — Los Angeles83.4%
- SEA to PHX — Phoenix79.2%
- SEA to SFO — San Francisco65.6%
- SEA to ANC — Anchorage75.2%
- SEA to DEN — Denver77.8%
- SEA to LAS — Las Vegas77.7%
- Alaska Airlines on-time record77.2%
- Delta Air Lines on-time record81.5%
- SkyWest Airlines on-time record86.1%
- United Airlines on-time record80.2%
- The best time of day to fly, according to 7.04 million flight records
- Do budget airlines really get delayed more? The numbers
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.