Carrier performance at one airport
UA→SEA
United Airlines at Seattle-Tacoma International
- Departures
- 8,804
- Period
- July 2025 to June 2026
- Routes
- 7
- Rank here
- #4 of 10
United Airlines at Seattle lands a B+, 3 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 a little over an hour on average. That is a workable record, not a spotless one. That rests on 8,804 flights, of which Envoy Air flew 691 at 86.9% on time.
Measured against the airport rather than the country, United Airlines runs about a point ahead of the 79.4% 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
80.2%
8,696 completed departures
Avg delay
76 min
Across delayed flights only
Cancelled
0.80%
At SEA, this carrier only
Rank here
#4
Of 10 carriers clearing the floor at SEA
These figures cover 8,804 flights between July 2025 and June 2026. The median arrival is 9 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 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 |
|---|---|---|---|---|---|
| Envoy Air | 691 | 86.9% | 71 min | 0.00% | A+ |
| SkyWest Airlines | 29,109 | 86.1% | 58 min | 0.71% | A+ |
| Delta Air Lines | 32,257 | 81.5% | 65 min | 1.05% | B |
| United Airlines (this page) | 8,804 | 80.2% | 76 min | 0.80% | B+ |
| American Airlines | 6,630 | 79.2% | 97 min | 2.07% | B |
| Alaska Airlines | 76,697 | 77.2% | 47 min | 1.05% | B |
| Frontier Airlines | 1,401 | 73.6% | 90 min | 2.28% | C |
| Southwest Airlines | 8,105 | 70.0% | 48 min | 0.41% | C+ |
| Hawaiian Airlines | 1,034 | 60.5% | 82 min | 1.26% | D |
| 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
Where United Airlines flies from SEA
United Airlines operates 7 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 SFO · San Francisco | 2,040 | 66.5% | 71 min | 0.83% | C+ |
| SEA to DEN · Denver | 1,905 | 87.5% | 73 min | 0.84% | A+ |
| SEA to ORD · Chicago | 1,534 | 79.8% | 81 min | 0.91% | B+ |
| SEA to IAH · Houston | 1,243 | 84.5% | 70 min | 0.56% | B+ |
| SEA to EWR · Newark | 997 | 81.4% | 88 min | 1.10% | B |
| SEA to IAD · Washington | 690 | 86.5% | 79 min | 0.72% | A+ |
| SEA to LAX · Los Angeles | 393 | 90.3% | 98 min | 0.00% | A+ |
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 16 points, against 27 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am2,014 flights88.2%
- 8am–11am1,220 flights79.4%
- 11am–2pm1,850 flights79.0%
- 2pm–5pm1,188 flights77.4%
- 5pm–8pm1,270 flights72.1%
- 8pm–5am1,262 flights81.0%
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 88.2% of the time, against 72.1% for the evening window. That is 16 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 2,014 flights scheduled in it.
Across the year
Seasonal pattern
July is the worst month at 72.5% on time, 16 points below September, the best at 88.5%. 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 1,034 flights.
Delay causes
What holds this operation up
- 43%National Airspace System
- 29%Late-arriving aircraft
- 26%Carrier
- 2%Extreme weather
- 0%Security
43% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 56,000 minutes out of 130,000, against a national NAS share of 21%. The split is drawn from 130,343 reported delay minutes.
Cancellations are rare at 0.80%, below the national 1.81% 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.
7.6% 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 a little over an hour kind, which a normal layover absorbs.
The sample behind these figures is 8,804 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.
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 88.5% on time and July 72.5%, a swing of 16 points. If the dates move at all, move them out of July before you think about anything else. 8,696 completed flights over 12 months sit behind that.
Common questions
United Airlines at SEA
How often is United Airlines at 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 19.8% of the 8,804 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on United Airlines at 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 United Airlines at SEA?
The 5am–8am departure window is the strongest at 88.2% on time. The 5pm–8pm window is the weakest at 72.1%, 16 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 United Airlines at SEA?
July is the weakest month at 72.5% on time, compared with 88.5% in September. 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
- United Airlines network-wide record
- Seattle-Tacoma International (SEA) all carriers
- SEA to SFO route record66.5%
- SEA to DEN route record87.5%
- SEA to ORD route record79.8%
- SEA to IAH route record84.5%
- 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.