Carrier performance at one airport
UA→SEA
United Airlines at Seattle-Tacoma International
- Departures
- 8,807
- Period
- June 2025 to May 2026
- Routes
- 7
- Rank here
- #4 of 10
United Airlines at Seattle lands a B+, 3 points better than the national rate of 77.4%. 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 8,807 flights, of which SkyWest Airlines flew 29,312 at 85.7% on time.
Measured against the airport rather than the country, United Airlines runs 2 points ahead of the 78.7% 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%
8,694 completed departures
Avg delay
76 min
Across delayed flights only
Cancelled
0.82%
At SEA, this carrier only
Rank here
#4
Of 10 carriers clearing the floor at SEA
These figures cover 8,807 flights between June 2025 and May 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. SkyWest Airlines arrives on time 85.7% of the time; Hawaiian Airlines manages 59.9%. Sample sizes sit next to every figure, because a two-point gap across 1,222 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlines | 29,312 | 85.7% | 58 min | 0.70% | A+ |
| Envoy Air | 646 | 84.9% | 65 min | 0.00% | B+ |
| Delta Air Lines | 32,222 | 81.5% | 65 min | 1.07% | B |
| United Airlines (this page) | 8,807 | 80.7% | 76 min | 0.82% | B+ |
| American Airlines | 6,544 | 78.8% | 87 min | 2.17% | B |
| Alaska Airlines | 76,709 | 75.8% | 47 min | 1.06% | B |
| Frontier Airlines | 1,416 | 72.9% | 90 min | 2.26% | C |
| Southwest Airlines | 8,101 | 70.8% | 49 min | 0.41% | C+ |
| JetBlue Airways | 414 | 60.7% | 109 min | 1.21% | D |
| Hawaiian Airlines | 1,222 | 59.9% | 80 min | 1.06% | D |
The spread between SkyWest and Hawaiian is 26 points, wide enough that it should decide the booking. On a hundred trips that is 26 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 | 2,012 | 71.6% | 73 min | 0.75% | C+ |
| SEA to DEN · Denver | 1,906 | 86.6% | 78 min | 0.84% | A+ |
| SEA to ORD · Chicago | 1,539 | 79.6% | 72 min | 0.91% | B+ |
| SEA to IAH · Houston | 1,251 | 83.2% | 71 min | 0.88% | B+ |
| SEA to EWR · Newark | 972 | 79.3% | 86 min | 1.13% | B |
| SEA to IAD · Washington | 732 | 85.5% | 76 min | 0.55% | A+ |
| SEA to LAX · Los Angeles | 393 | 90.3% | 94 min | 0.25% | 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 15 points, against 26 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am2,003 flights89.1%
- 8am–11am1,207 flights82.6%
- 11am–2pm1,847 flights77.8%
- 2pm–5pm1,173 flights77.8%
- 5pm–8pm1,255 flights73.9%
- 8pm–5am1,322 flights79.2%
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 89.1% of the time, against 73.9% for the evening window. That is 15 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on.
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.
Delay causes
What holds this operation up
- 41%National Airspace System
- 30%Late-arriving aircraft
- 27%Carrier
- 2%Extreme weather
- 0%Security
41% 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 52,000 minutes out of 127,000, against a national NAS share of 21%.
Cancellations are rare at 0.82%, below the national 1.80% 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.
7.5% of arrivals land an hour or more late, close to the national 8.2%. 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 8,807 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.
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 19.3% of the 8,807 flights in this analysis, against 22.6% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on United Airlines at SEA?
SkyWest Airlines leads at 85.7% on time across 29,312 flights. Hawaiian Airlines is at the other end on 59.9%, a gap of 26 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 89.1% on time. The 5pm–8pm window is the weakest at 73.9%, 15 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
Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.