About 1 in 4 UA 2661 flights from San Francisco arrived 15+ minutes late, diverted or cancelled over the past year (23%); 0.0% were cancelled. The typical flight landed 0 minutes early.
UA 2661: SFO → ONT
Scheduled to leave San Francisco at 10:40 a.m. local time. Over the past year it arrived on time 77% of the time (195 flights), worse than other UA flights on the route at that hour (81%). Last seen in the data Aug 31, 2026.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 29 | 72% |
| Tuesday | 25 | 80% |
| Wednesday | 25 | 80% |
| Thursday | 29 | 79% |
| Friday | 29 | 79% |
| Saturday | 29 | 72% |
| Sunday | 29 | 76% |
Why it was late
All flights SFO → ONT · Connecting off UA 2661? Check the risk
UA 2661: PHL → SFO
Scheduled to leave Philadelphia at 6:00 a.m. local time. Over the past year it arrived on time 90% of the time (144 flights), better than other UA flights on the route at that hour (84%). Last seen in the data Aug 31, 2026.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 23 | 91% |
| Tuesday | 20 | 90% |
| Wednesday | 19 | — |
| Thursday | 22 | 95% |
| Friday | 22 | 91% |
| Saturday | 16 | — |
| Sunday | 22 | 77% |
Why it was late
All flights PHL → SFO · Connecting off UA 2661? Check the risk
Questions
How often is UA 2661 from SFO to ONT late?
United Airlines 2661 from San Francisco, CA to Ontario, CA arrived 15 or more minutes late, was diverted or was cancelled on 23% of 195 scheduled flights between September 2025 and August 2026. 0.0% were cancelled.
How often is UA 2661 from PHL to SFO late?
United Airlines 2661 from Philadelphia, PA to San Francisco, CA arrived 15 or more minutes late, was diverted or was cancelled on 10% of 144 scheduled flights between September 2025 and August 2026. 0.0% were cancelled.
Flight numbers change. Figures cover flights with this airline, number and route only. "Likely range" is the 95% interval for the true on-time rate given the number of flights. This is history, not live status: check United Airlines for today's flight. Method.