Carrier route record
UASFO→ONT
United Airlines · San Francisco to Ontario
- Flights
- 1,008
- Period
- July 2025 to June 2026
- Share of route
- 78%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on SFO to ONT lands a B+, 3 points better than the national rate of 77.6%. About one flight in five arrives 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 1,008 flights, with a median arrival 4 minutes early.
The US average over the same twelve months is 77.6%, so there is little to separate United on SFO to ONT from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
81.0%
Arrivals under 15 minutes late, of 1,005 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.30%
National rate is 1.81%
Whole route
76.8%
Every carrier on SFO to ONT, 1,291 flights
These figures cover 1,008 flights between July 2025 and June 2026. The median arrival is 4 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
United against every carrier on SFO to ONT
United flew 1,008 of the 1,291 flights on SFO to ONT, most of the route. Its 81.0% on time is 4 points better than the route as a whole, which runs 76.8%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from United at 81.0% to Frontier at 56.7%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines (this page) | 1,008 | 81.0% | 55 min | 0.30% | B+ |
| SkyWest Airlinesthin sample | 106 | 68.9% | 77 min | 2.83% | C |
| Frontier Airlinesthin sample | 177 | 56.7% | 107 min | 3.39% | D− |
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 26 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am279 flights84.2%
- 11am–2pm90 flights80.0%
- 2pm–5pm302 flights82.7%
- 5pm–8pm41 flights100.0%
- 8pm–5am296 flights73.9%
Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is the strongest at 100.0% on time. The full set of windows spans 26 points.
Across the year
United on SFO to ONT through the year
July is the worst month at 72.7% on time, 17 points below March, the best at 89.4%. 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. April was the busiest month here, with 108 flights.
Across the week, Tuesday is the strongest day at 83.6% on time and Friday the weakest at 77.0%. 7 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 51% of the 11,000 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.
- 51%Late-arriving aircraft
- 31%Carrier
- 19%National Airspace System
51% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 11,000 reported delay minutes here, that single category outweighs weather by 51 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 10,535 reported delay minutes.
Cancellations are rare at 0.30%, 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.
Connections and stage length
What a delay here costs
5.2% 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 last about an hour, which a normal layover absorbs.
At 363 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5pm–8pm window matters as much as it does.
The return leg is a different operation and performs like one: it runs 70.7% on time across 1,007 flights, 10 points below 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 10 points of difference.
One caution: this is a thin sample. 1,008 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking United on SFO to ONT
Put together: treat all of this as provisional. 1,008 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 81.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,005 completed flights over 12 months sit behind that.
Related
Where to go next
- SFO to ONT, every carrier
- United on ONT to SFO, the return leg
- SkyWest Airlines on SFO to ONT68.9%
- Frontier Airlines on SFO to ONT56.7%
- United Airlines network-wide record
- San Francisco International (SFO) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.