Carrier performance at one airport
UA→SEA
United Airlines at Seattle-Tacoma International
- Departures
- 8,683
- Period
- September 2025 to August 2026
- Routes
- 7
- Rank here
- #4 of 10
United Airlines 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 a little over an hour on average. That rests on 8,683 flights, of which Envoy Air flew 760 at 85.3% on time.
Measured against the airport rather than the country, United Airlines runs half 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
79.9%
8,580 completed departures
Avg delay
74 min
Across delayed flights only
Cancelled
0.75%
At SEA, this carrier only
Rank here
#4
Of 10 carriers clearing the floor at SEA
These figures cover 8,683 flights between September 2025 and August 2026. The median arrival is 10 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 | 32,382 | 80.7% | 64 min | 1.11% | B |
| United Airlines (this page) | 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 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 | 2,062 | 59.1% | 67 min | 0.82% | D+ |
| SEA to DEN · Denver | 1,910 | 88.2% | 74 min | 0.58% | A+ |
| SEA to ORD · Chicago | 1,488 | 81.6% | 88 min | 0.81% | B+ |
| SEA to IAH · Houston | 1,230 | 87.9% | 78 min | 0.16% | A+ |
| SEA to EWR · Newark | 990 | 84.2% | 87 min | 1.92% | B |
| SEA to IAD · Washington | 626 | 91.4% | 76 min | 0.64% | A+ |
| SEA to LAX · Los Angeles | 375 | 88.8% | 72 min | 0.00% | A+ |
Flight by flight
United Airlines flight numbers from SEA
6 United Airlines flight numbers leaving SEA flew their main route often enough to have a record of their own. Grouped by destination.
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 17 points, against 32 points between the best and worst carrier.
- 5am–8am1,965 flights87.2%
- 8am–11am1,301 flights75.9%
- 11am–2pm1,842 flights79.3%
- 2pm–5pm1,192 flights77.8%
- 5pm–8pm1,208 flights70.2%
- 8pm–5am1,175 flights85.5%
Scale runs 60% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 87.2% of the time, against 70.2% for the evening window. That is 17 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 1,965 flights scheduled in it.
Across the year
Seasonal pattern
July is the worst month at 70.9% on time, 18 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 978 flights.
Delay causes
What holds this operation up
- 47%National Airspace System
- 27%Late-arriving aircraft
- 25%Carrier
- 2%Extreme weather
- 0%Security
47% 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 60,000 minutes out of 128,000, against a national NAS share of 21%. The split is drawn from 127,655 reported delay minutes.
Cancellations are rare at 0.75%, below the national 1.89% 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.
7.4% 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 a little over an hour, which a normal layover absorbs.
The sample behind these figures is 8,683 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 70.9%, a swing of 18 points. If the dates move at all, move them out of July before you think about anything else. 8,580 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 arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 20.1% of the 8,683 flights in this analysis, against 22.7% 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 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 United Airlines at SEA?
The 5am–8am departure window is the strongest at 87.2% on time. The 5pm–8pm window is the weakest at 70.2%, 17 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 70.9% on time, compared with 88.5% in September. Across the year that is 18 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.