Carrier route record
UAONT→SFO
United Airlines · Ontario to San Francisco
- Flights
- 1,007
- 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 ONT to SFO sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 7 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 1,007 flights, with a median arrival 2 minutes early.
The national on-time rate over the same period is 77.6%, so United on ONT to SFO runs 7 points behind the country as a whole. Across a thousand flights that is about 69 extra late arrivals.
Key figures
On time
70.7%
Arrivals under 15 minutes late, of 1,003 completed flights
Avg delay
66 min
Across delayed arrivals only, not all flights
Cancelled
0.40%
National rate is 1.81%
Whole route
64.9%
Every carrier on ONT to SFO, 1,290 flights
These figures cover 1,007 flights between July 2025 and June 2026. Beyond the headline rate, 9.4% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
United against every carrier on ONT to SFO
United flew 1,007 of the 1,290 flights on ONT to SFO, most of the route. Its 70.7% on time is 6 points better than the route as a whole, which runs 64.9%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from United at 70.7% to Frontier at 41.6%. 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) | 1,007 | 70.7% | 66 min | 0.40% | C+ |
| SkyWest Airlinesthin sample | 106 | 48.1% | 68 min | 1.89% | F |
| Frontier Airlinesthin sample | 177 | 41.6% | 71 min | 2.26% | F |
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 42 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–8am310 flights90.9%
- 8am–11am49 flights49.0%
- 11am–2pm231 flights72.7%
- 2pm–5pm138 flights66.7%
- 5pm–8pm276 flights52.2%
- 8pm–5am3 flights—
Scale runs 40% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 90.9% of the time, against 49.0% for the morning window. That is 42 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 310 flights scheduled in it.
Across the year
United on ONT to SFO through the year
Delays peak in May, when the on-time rate falls to 53.7%. March is the strongest month at 92.4%. Moving a flexible trip across that boundary buys 39 points. April was the busiest month here, with 108 flights.
Across the week, Tuesday is the strongest day at 79.0% on time and Wednesday the weakest at 65.7%. 13 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. National Airspace System accounts for 55% of the 19,000 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.
- 55%National Airspace System
- 23%Late-arriving aircraft
- 20%Carrier
- 2%Extreme weather
55% 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 11,000 minutes out of 19,000, against a national NAS share of 21%. The split is drawn from 19,423 reported delay minutes.
Cancellations are rare at 0.40%, 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
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.4% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
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 5am–8am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 81.0% on time across 1,008 flights, 10 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 10 points of difference.
One caution: this is a thin sample. 1,007 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 ONT to SFO
Put together: treat all of this as provisional. 1,007 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 70.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,003 completed flights over 12 months sit behind that.
Related
Where to go next
- ONT to SFO, every carrier
- United on SFO to ONT, the return leg
- SkyWest Airlines on ONT to SFO48.1%
- Frontier Airlines on ONT to SFO41.6%
- United Airlines network-wide record
- San Francisco International (SFO) delay statistics
- The best time of day to fly, according to 7.04 million flight records
- How often a connection fails at the major US hubs
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.