Route reliability record
SFO→ONT
San Francisco to Ontario
- Flights
- 1,291
- Period
- July 2025 to June 2026
- Distance
- 363 mi
- Carriers
- 3
This route lands a B+, about a point worse than the national rate of 77.6%. About one flight in four arrives 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 1,291 SFO to ONT flights, with a median arrival 3 minutes early.
Best time to fly SFO to ONT: a 5pm–8pm departure, ideally on a Tuesday. Flights in that window arrived on time 92.3% of the time and Tuesday flights 83.1%, against 76.8% for the route overall.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.8%
Arrivals under 15 minutes late, of 1,279 completed flights
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
0.93%
National rate is 1.81%
Best carrier
United
81.0% on time across 1,008 flights
These figures cover 1,291 flights between July 2025 and June 2026. The median arrival is 3 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
Which airline is most reliable on SFO to ONT
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 | 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− |
Best ways to make this trip
The most reliable ways to fly San Francisco to Ontario
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 5 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SJC → LAXSan Jose to Los Angeles | SkyWest Airlines | 92.2% | 92.6% | 0.39% | 5am–8am, Thu | OO 3979 07:00 |
| 2. SJC → LAXSan Jose to Los Angeles | Delta Air Lines | 89.5% | 92.3% | 3.08% | 11am–2pm, Sun | — |
| 3. SJC → SNASan Jose to Santa Ana | Southwest Airlines | 86.3% | 87.0% | 0.83% | 5am–8am, Sat (route) | — |
| 4. OAK → LGBOakland to Long Beach | Southwest Airlines | 86.1% | 86.3% | 0.25% | 5am–8am, Tue | — |
| 5. SJC → LGBSan Jose to Long Beach | Southwest Airlines | 85.4% | 85.5% | 0.16% | 5am–8am, Wed | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
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–11am359 flights82.4%
- 11am–2pm101 flights76.2%
- 2pm–5pm361 flights81.0%
- 5pm–8pm52 flights92.3%
- 8pm–5am418 flights66.4%
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is the strongest at 92.3% on time. The full set of windows spans 26 points.
Across the year
When delays peak on this route
This route's year swings by 22 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
Delays peak in November, when the on-time rate falls to 68.0%. March is the strongest month at 90.3%. Moving a flexible trip across that boundary buys 22 points. May was the busiest month here, with 127 flights.
Across the week, Tuesday is the strongest day at 83.1% on time and Friday the weakest at 71.7%. 11 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 55% of the 21,000 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%Late-arriving aircraft
- 30%Carrier
- 13%National Airspace System
- 3%Extreme weather
55% 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 21,000 reported delay minutes here, that single category outweighs weather by 21 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 20,927 reported delay minutes.
Cancellations sit at 0.93% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here actually costs
7.4% 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 a little over 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 64.9% on time across 1,290 flights, 12 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 12 points of difference.
The sample behind these figures is 1,291 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.
Work out the risk of missing a connection in ONT after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. March runs 90.3% on time and November 68.0%, a swing of 22 points. If the dates move at all, move them out of November before you think about anything else. 1,279 completed flights over 12 months sit behind that.
Common questions
SFO to ONT questions
How often is SFO to ONT delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.2% of the 1,291 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
How reliable is SFO to ONT compared with the rest of the country?
76.8% of flights arrive on time here against a national 77.6%, a difference of about a point against it. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on SFO to ONT?
The 5pm–8pm departure window is the strongest at 92.3% on time. The 8pm–5am window is the weakest at 66.4%, 26 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 November delays on SFO to ONT?
November is the weakest month at 68.0% on time, compared with 90.3% in March. Across the year that is 22 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
- ONT to SFO — the return legseparate record
- San Francisco International (SFO) delay statistics
- United Airlines on SFO to ONT81.0%
- SkyWest Airlines on SFO to ONT68.9%
- Frontier Airlines on SFO to ONT56.7%
- SFO to LAX, a related route73.9%
- PHX to ONT, a related route77.7%
- SFO to SEA, a related route73.7%
- United Airlines on-time record81.0%
- SkyWest Airlines on-time record68.9%
- Frontier Airlines on-time record56.7%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. SFO to ONT and ONT to SFO are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.