Carrier route record
F9ONT→SFO
Frontier Airlines · Ontario to San Francisco
- Flights
- 177
- Period
- July 2025 to June 2026
- Share of route
- 14%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Frontier Airlines.
Frontier on ONT to SFO earns an F, which is as low as this site's scale goes for a reason. Only 41.6% of flights arrive inside the 15-minute window, 36 points worse than the national rate of 77.6%. Late arrivals average a little over an hour. Treat any tight connection here as a coin flip. That rests on 177 flights, with a median arrival 28 minutes late.
The national on-time rate over the same period is 77.6%, so Frontier on ONT to SFO runs 36 points behind the country as a whole. Across a thousand flights that is about 360 extra late arrivals.
Key figures
On time
41.6%
Arrivals under 15 minutes late, of 173 completed flights
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
2.26%
National rate is 1.81%
Whole route
64.9%
Every carrier on ONT to SFO, 1,290 flights
These figures cover 177 flights between July 2025 and June 2026. Beyond the headline rate, 25.4% 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
Frontier against every carrier on ONT to SFO
Frontier flew 177 of the 1,290 flights on ONT to SFO, about 14% of it. Its 41.6% on time is 23 points worse than the route as a whole, which runs 64.9%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from United at 70.7% to Frontier at 41.6%. One 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 | 1,007 | 70.7% | 66 min | 0.40% | C+ |
| SkyWest Airlinesthin sample | 106 | 48.1% | 68 min | 1.89% | F |
| Frontier Airlines (this page)thin sample | 177 | 41.6% | 71 min | 2.26% | F |
Departure window
When Frontier runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 11 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–11am33 flights31.2%
- 11am–2pm—
- 2pm–5pm—
- 5pm–8pm4 flights—
- 8pm–5am140 flights42.3%
Scale runs 25% to 50%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is the strongest at 42.3% on time. The full set of windows spans 11 points.
Across the year
Frontier on ONT to SFO through the year
- Jul–Sep 202545 flights47.7%
- Oct–Dec 202554 flights66.0%
- Jan–Mar 202615 flights—
- Apr–Jun 202663 flights9.7%
Scale runs 0% to 70%. Rows with fewer than 30 flights show a dash.
Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 41.6% on time across 177 flights.
Frontier on ONT to SFO did not run the same all year. Its best quarter was Oct–Dec 2025 at 66.0% on time and its weakest Apr–Jun 2026 at 9.7%, a swing of 56 points on roughly 59 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
Across the week, Friday is the strongest day at 52.4% on time and Monday the weakest at 33.3%. 19 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Frontier runs late on this route
One category carries most of the weight here. National Airspace System accounts for 61% of the 7,153 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.
- 61%National Airspace System
- 35%Late-arriving aircraft
- 4%Carrier
35% 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 7,153 reported delay minutes here, that single category outweighs weather by 35 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 7,153 reported delay minutes.
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 4,380 minutes out of 7,153, against a national NAS share of 21%.
Cancellations sit at 2.26% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
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. 25.4% 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 8pm–5am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 56.7% on time across 177 flights, 15 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 15 points of difference.
One caution: this is a thin sample. 177 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 Frontier on ONT to SFO
Put together: treat all of this as provisional. 177 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 41.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 173 completed flights over 12 months sit behind that.
Related
Where to go next
- ONT to SFO, every carrier
- Frontier on SFO to ONT, the return leg
- United Airlines on ONT to SFO70.7%
- SkyWest Airlines on ONT to SFO48.1%
- Frontier 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.