Carrier route record
UASEA→SFO
United Airlines · Seattle to San Francisco
- Flights
- 2,062
- Period
- September 2025 to August 2026
- Share of route
- 30%
- Carriers
- 5
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with United Airlines.
United on SEA to SFO draws a D+. Roughly one flight in two arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 2,062 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,039 at 69.9% on time.
SkyWest Airlines is the most reliable of the three carriers covered here at 69.9% on time across 1,039 flights.
Key figures
On time
59.1%
Arrivals under 15 minutes late, of 2,043 completed flights
Avg delay
67 min
Across delayed arrivals only, not all flights
Cancelled
0.82%
National rate is 1.89%
Whole route
59.8%
Every carrier on SEA to SFO, 6,817 flights
These figures cover 2,062 flights between September 2025 and August 2026. Beyond the headline rate, 14.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
United against every carrier on SEA to SFO
United flew 2,062 of the 6,817 flights on SEA to SFO, about 30% of it. Its 59.1% on time is about level with the route as a whole at 59.8%. Ranked by on-time rate it is number four of five carriers on the route, where the range runs from Southwest at 100.0% to Alaska at 56.0%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 69.9% of the time; Alaska Airlines manages 56.0%. Sample sizes sit next to every figure, because a two-point gap across 2,727 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlinesthin sample | 4 | 100.0% | — | 0.00% | A+ |
| SkyWest Airlines | 1,039 | 69.9% | 52 min | 1.06% | C |
| Delta Air Lines | 985 | 60.5% | 54 min | 1.73% | D |
| United Airlines (this page) | 2,062 | 59.1% | 67 min | 0.82% | D+ |
| Alaska Airlines | 2,727 | 56.0% | 52 min | 1.14% | D |
The spread between SkyWest and Alaska is 14 points, wide enough that it should decide the booking. On a hundred trips that is 14 more arrivals inside the on-time window.
Flight by flight
United flight numbers on SEA to SFO
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Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 36 points, against 14 points between the best and worst carrier.
- 5am–8am356 flights59.1%
- 8am–11am400 flights43.8%
- 11am–2pm397 flights63.3%
- 2pm–5pm241 flights79.3%
- 5pm–8pm668 flights58.6%
- 8pm–5am—
Scale runs 35% to 85%. Rows with fewer than 30 flights show a dash.
The best window here is not the first bank but the 2pm–5pm slot at 79.3% on time, ahead of 8am–11am at 43.8%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 5pm–8pm window is the busiest, with 668 flights scheduled in it.
Across the year
United on SEA to SFO through the year
June is the worst month at 29.5% on time, 55 points below September, the best at 84.7%. 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 210 flights.
Across the week, Saturday is the strongest day at 72.4% on time and Monday the weakest at 49.4%, a spread of 23 points.
Arrival by arrival
How late United on SEA to SFO runs when it is late
The 835 late arrivals split 243 under half an hour, 299 between 30 and 60 minutes, and 293 an hour or more.
- 15+ min early463 flights22.7%
- Within 15 min745 flights36.5%
- 15–29 min late243 flights11.9%
- 30–59 min late299 flights14.6%
- 1–2 hours late191 flights9.3%
- 2+ hours late102 flights5.0%
Scale runs 0% to 100%.
Share of 2,043 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 710 departures that left 15 minutes late or more, only 53 made it up before arrival. In the other direction, 178 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SFO.
The worst days
Worst days for United on SEA to SFO
The latest arrival of the period was on 23 February 2026, 12 hours 17 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. On four of the five worst days the largest share was filed as carrier-caused (crew, maintenance, fuelling, baggage).
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 23 February 2026 | 12 hours 17 minutes | Late-arriving aircraft |
| 23 June 2026 | 9 hours 42 minutes | Carrier |
| 2 August 2026 | 8 hours 38 minutes | Carrier |
| 5 October 2025 | 7 hours 50 minutes | Carrier |
| 28 July 2026 | 6 hours 14 minutes | Carrier |
Delay causes
Why United runs late on this route
National Airspace System accounts for 61% of the 56,000 delay minutes carriers reported here, and the remaining four split what is left.
- 61%National Airspace System
- 21%Late-arriving aircraft
- 16%Carrier
- 1%Extreme weather
- 0%Security
61% 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 34,000 minutes out of 56,000, against a national NAS share of 21%. The split is drawn from 55,890 reported delay minutes.
Cancellations are rare at 0.82%, 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.
Connections and stage length
What a delay here costs
14.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
The 679 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty.
The return leg is a different operation and performs like one: it runs 75.1% on time across 2,063 flights, 16 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 16 points of difference.
The sample behind these figures is 2,062 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.
What to do with this
Booking United on SEA to SFO
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 84.7% on time and June 29.5%, a swing of 55 points. If the dates move at all, move them out of June before you think about anything else. 2,043 completed flights over 12 months sit behind that.
Related
Where to go next
- SEA to SFO, every carrier
- United on SFO to SEA, the return leg
- SkyWest Airlines on SEA to SFO69.9%
- Delta Air Lines on SEA to SFO60.5%
- Alaska Airlines on SEA to SFO56.0%
- United Airlines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- San Francisco International (SFO) delay statistics
- Same route, different airline: where the carrier you pick matters most
- The best time of day to fly, according to 7.05 million flight records
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.