About 1 in 5 UA 643 flights from San Francisco arrived 15+ minutes late, diverted or cancelled over the past year (21%); 0.0% were cancelled. The typical flight landed 4 minutes early.
UA 643: SFO → SNA
Scheduled to leave San Francisco at 10:40 a.m. local time. Over the past year it arrived on time 79% of the time (297 flights), in line with 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 | 43 | 77% |
| Tuesday | 43 | 86% |
| Wednesday | 43 | 86% |
| Thursday | 42 | 69% |
| Friday | 42 | 71% |
| Saturday | 42 | 86% |
| Sunday | 42 | 76% |
Why it was late
All flights SFO → SNA · Connecting off UA 643? Check the risk
UA 643: SNA → IAH
Scheduled to leave Santa Ana at 3:05 p.m. local time. Over the past year it arrived on time 86% of the time (232 flights), in line with other UA flights on the route at that hour (85%). Last seen in the data Aug 31, 2026.
Usually United Airlines's last flight of the day from Santa Ana to Houston (100% of days). United Airlines's last SNA–IAH flight was cancelled 0.0% of the time, against 0.0% for its earlier ones. If it's cancelled, the next United Airlines flight is usually around 7:45 a.m. the next morning.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 34 | 91% |
| Tuesday | 33 | 94% |
| Wednesday | 33 | 91% |
| Thursday | 33 | 91% |
| Friday | 33 | 79% |
| Saturday | 32 | 78% |
| Sunday | 34 | 79% |
Why it was late
All flights SNA → IAH · Connecting off UA 643? Check the risk
UA 643: LAS → SFO
Scheduled to leave Las Vegas at 6:00 a.m. local time. Over the past year it arrived on time 97% of the time (230 flights), in line with other UA flights on the route at that hour (97%). Last seen in the data Aug 31, 2026.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 34 | 100% |
| Tuesday | 34 | 100% |
| Wednesday | 29 | 97% |
| Thursday | 33 | 94% |
| Friday | 34 | 97% |
| Saturday | 34 | 94% |
| Sunday | 32 | 97% |
Why it was late
All flights LAS → SFO · Connecting off UA 643? Check the risk
Questions
How often is UA 643 from SFO to SNA late?
United Airlines 643 from San Francisco, CA to Santa Ana, CA arrived 15 or more minutes late, was diverted or was cancelled on 21% of 297 scheduled flights between September 2025 and August 2026. 0.0% were cancelled.
How often is UA 643 from SNA to IAH late?
United Airlines 643 from Santa Ana, CA to Houston, TX arrived 15 or more minutes late, was diverted or was cancelled on 14% of 232 scheduled flights between September 2025 and August 2026. 0.0% were cancelled.
How often is UA 643 from LAS to SFO late?
United Airlines 643 from Las Vegas, NV to San Francisco, CA arrived 15 or more minutes late, was diverted or was cancelled on 3% of 230 scheduled flights between September 2025 and August 2026. 0.9% 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.