Route on-time record
ONT to SFO: most on-time flights and the best time to fly
Ontario (Ontario International Airport) to San Francisco (San Francisco International Airport). 1,274 nonstop flights in Jun 2025 to May 2026, 69% arrived within 15 minutes and 0.9% were cancelled. The most reliable flight number was United 2363 at 6:00 AM.
Flying on a specific date? We’ll adjust for the month, the weekday and the forecast.
ONT → SFO
Ontario to San Francisco: 1,274 nonstop flights a year
On time (12 months)
69%
Cancelled
0.9%
avg delay 21 min
Best time to leave
Before 9 AM
88% on time vs 45% 9 AM to noon
Most reliable airline
United
72% chance on time
Lowest nonstop fare seen in the next two months: $46 (Frontier 1159 on 2026-11-12). Fares open on our travel partner (Aviasales). Pick the flight number you chose here.
Most reliable nonstop flights
Ranked by the chance the flight operates and arrives within 15 minutes of schedule, from Jun 2025 to May 2026 records.
#1 · United 2363
6:00 AM → 7:29 AM1h 29m nonstop
Local times, typical schedule. Last flown 2026-05-31.
90%
chance on time
- On time (history)
- 91%
- Cancelled
- 1.4%
- Avg arrival delay
- 8 min
- Arrived on time 91% of the time (138 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 88% on time; 9 AM to noon: 45%).
- Lands inside SFO's trouble window: 61% of its 333 ground stops and delay programs started between 7 AM and 1 PM.
Moderate track record · 138 flights
Find United 2363 fares Opens this date on Aviasales#2 · United 1375
1:27 PM → 3:13 PM1h 29m nonstop
Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as United 1503; its record covers all of them.
77%
chance on time
- On time (history)
- 72%
- Cancelled
- 0.0%
- Avg arrival delay
- 21 min
- Arrived on time 72% of the time (88 flights, Jun 2025 to May 2026).
- Never cancelled in 88 scheduled flights.
Moderate track record · 88 flights
Find United 1375 fares Opens this date on Aviasales#3 · United 1851
10:37 AM → 12:07 PM1h 30m nonstop
Local times, typical schedule. Last flown 2026-05-18.
62%
chance on time
- On time (history)
- 33%
- Cancelled
- 0.0%
- Avg arrival delay
- 43 min
- Arrived on time 33% of the time (15 flights, Jun 2025 to May 2026).
- Leaves in this route's least on-time window (9 AM to noon: 45% on time; Before 9 AM: 88%).
- Lands inside SFO's trouble window: 61% of its 333 ground stops and delay programs started between 7 AM and 1 PM.
- Short track record (15 flights), so its score leans on the airline's record at this hour.
Limited track record · 15 flights
Find United 1851 fares Opens this date on Aviasales#4 · United 1665
6:37 PM → 8:10 PM1h 29m nonstop
Local times, typical schedule. Last flown 2026-05-20.
57%
chance on time
- On time (history)
- 51%
- Cancelled
- 0.0%
- Avg arrival delay
- 26 min
- Arrived on time 51% of the time (71 flights, Jun 2025 to May 2026).
- Never cancelled in 71 scheduled flights.
Moderate track record · 71 flights
Find United 1665 fares Opens this date on Aviasales#5 · United 2248
11:05 AM → 12:35 PM1h 30m nonstop
Local times, typical schedule. Last flown 2026-04-29.
55%
chance on time
- On time (history)
- 34%
- Cancelled
- 0.0%
- Avg arrival delay
- 42 min
- Arrived on time 34% of the time (29 flights, Jun 2025 to May 2026).
- Leaves in this route's least on-time window (9 AM to noon: 45% on time; Before 9 AM: 88%).
- Lands inside SFO's trouble window: 61% of its 333 ground stops and delay programs started between 7 AM and 1 PM.
- Short track record (29 flights), so its score leans on the airline's record at this hour.
Limited track record · 29 flights
Find United 2248 fares Opens this date on Aviasales#6 · Frontier 2677
8:59 AM → 10:38 AM1h 40m nonstop
Local times, typical schedule. Last flown 2026-05-31.
50%
chance on time
- On time (history)
- 51%
- Cancelled
- 3.1%
- Avg arrival delay
- 34 min
- Arrived on time 51% of the time (156 flights, Jun 2025 to May 2026).
- Cancelled 3.1% of the time (5 of 161).
- Leaves in this route's most on-time window (Before 9 AM: 88% on time; 9 AM to noon: 45%).
- Lands inside SFO's trouble window: 61% of its 333 ground stops and delay programs started between 7 AM and 1 PM.
Moderate track record · 156 flights
Find Frontier 2677 fares Opens this date on Aviasales#7 · SkyWest 5624 · sold as United Express, Delta Connection, American Eagle or Alaska
6:39 PM → 8:09 PM1h 30m nonstop
Local times, typical schedule. Last flown 2026-05-31.
44%
chance on time
- On time (history)
- 0%
- Cancelled
- 9.1%
- Avg arrival delay
- 56 min
- Arrived on time 0% of the time (10 flights, Jun 2025 to May 2026).
- Short track record (10 flights), so its score leans on the airline's record at this hour.
Limited track record · 10 flights
Find 6:39 PM flight fares Opens this date on Aviasales
Airlines on this route
Season-adjusted chance of operating and arriving on time.
- United Airlines72%
1,036 flights · 73% on time as flown · 0.4% cancel
- SkyWest Airlines (sold as United Express, Delta Connection, American Eagle or Alaska)65%
77 flights · 63% on time as flown · 1.5% cancel
- Frontier Airlines56%
161 flights · 51% on time as flown · 2.0% cancel
On time by departure time
All airlines, scheduled local departure, Jun 2025 to May 2026.
- Before 9 AM88%
348 flights · avg delay 10 min
- 9 AM to noon45%
111 flights · avg delay 33 min
- Noon to 3 PM79%
341 flights · avg delay 13 min
- 6 to 9 PM53%
352 flights · avg delay 34 min
- After 9 PM59%
122 flights · avg delay 32 min
Best day: Tuesday (80%). Worst: Monday (66%).
Smarter routing
Nearby airports that run more on time
LGB → OAK 89% chance on time
Long Beach International Airport to Oakland San Francisco Bay Airport · 1,649 flights a year · 47 mi from your airports · yours: 69%
LGB → SJC 87% chance on time
Long Beach International Airport to Norman Y. Mineta San Jose International Airport · 1,222 flights a year · 66 mi from your airports · yours: 69%
BUR → SJC 87% chance on time
Hollywood Burbank/Bob Hope Airport to Norman Y. Mineta San Jose International Airport · 2,218 flights a year · 74 mi from your airports · yours: 69%
LAX → SJC 87% chance on time
Los Angeles International Airport to Norman Y. Mineta San Jose International Airport · 4,400 flights a year · 77 mi from your airports · yours: 69%
On time by month
All airlines, Jun 2023 to May 2026. Several years per month, so one stormy season doesn't define a month. Travel-month estimates use this seasonal pattern.
What delays this route
- Air traffic control and airport volume54%
- Late-arriving aircraft29%
- Airline (crew, maintenance, boarding)14%
- Severe weather3%
Share of delay minutes by the cause airlines report to the US DOT.
Historical odds, not a guarantee. Built from the US DOT Bureau of Transportation Statistics on-time reports (Jun 2025 to May 2026), FAA ground stop and delay program advisories, and 20 years of airport weather observations. Covers US airlines that report to the DOT; schedules are flights operated recently, so confirm times when you book. ATIS Alerts is not affiliated with any airline. Fares are what Aviasales travelers saw in recent searches (USD, one way, 1 adult), not live quotes; the partner site shows the current price. Fare links go to our travel partner and may earn us a commission at no cost to you. Affiliate disclosure
ONT to SFO questions
- What time of day is best to fly ONT to SFO?
- Before 9 AM: 88% of flights arrived on time, against 45% for departures 9 AM to noon. Later flights inherit delays from earlier ones, so the first departures of the day usually run best.
- Which airline is most on time from ONT to SFO?
- United, with a season-adjusted 72% chance of operating and arriving on time over 1,036 flights. The adjustment compares each airline with what the route did in the months it flew, so a carrier that skipped a stormy month gets no free credit.
- What is the worst month for delays on ONT to SFO?
- May (59% on time); the best was January (82%), averaged over Jun 2023 to May 2026.
- Is this a prediction for my flight?
- No. These are historical odds from the US DOT on-time reports, FAA advisories and airport weather records. Check your flight status and the FAA delay board on the day you fly.
More routes from ONT
- SFO to ONT (return)
- ONT to PHX 83%
- ONT to DEN 79%
- ONT to SEA 86%
- ONT to LAS 78%
- ONT to DFW 78%
- ONT to SMF 86%
- ONT to OAK 87%
- ONT to SJC 86%
- ONT to SLC 91%
- ONT to ATL 90%
- ONT to PDX 88%
- ONT to IAH 85%
Live status: FAA delays and ground stops