Flight number record
UA 643
United Airlines · San Francisco to Santa Ana
- Route
- SFO → SNA
- Departs
- 10:40
- Flights
- 297
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 643, check with United Airlines.
UA 643 lands a B+, 2 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by roughly 45 minutes on average. That rests on 297 flights, with a median arrival 4 minutes early.
Key figures
On time
78.8%
Arrivals under 15 minutes late, of 297 completed flights
Avg delay
44 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.89%
1 hour+ late
3.4%
National rate is 8.3%
These figures cover 297 flights between September 2025 and August 2026. The median arrival is 4 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.
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Schedule
When UA 643 flies
UA 643 flies SFO to SNA without a single fixed slot. Its most common scheduled departure was 10:40, used on 61 of 297 flights, with 10:23 (47 flights) and 10:34 (32 flights) next.
- Departs 10:4061 flights20.5%
- Departs 10:2347 flights15.8%
- Departs 10:3432 flights10.8%
Scale runs 0% to 100%.
Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.
A 10:40 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 83.9%, and UA 643 runs 5 points worse at 78.8%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
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Against the route
UA 643 next to SFO to SNA
Every carrier on SFO to SNA combined arrived on time 77.4% of the time across 4,701 flights, so UA 643 is about level with it. United flew 1,012 flights on the same city pair under all its flight numbers, including this one, and those ran 82.5% on time. Across its whole network United Airlines managed 78.8%, close to this flight's figure.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 643thin sample | 297 | 78.8% | 44 min | 0.00% | B+ |
| All United Airlines on SFO–SNA | 1,012 | 82.5% | 52 min | 0.30% | B+ |
| All carriers on SFO–SNA | 4,701 | 77.4% | 61 min | 1.43% | B |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 643 quarter by quarter
Quarter by quarter UA 643 held fairly steady: 80.0% in Oct–Dec 2025, 80.0% in Jan–Mar 2026, 73.6% in Apr–Jun 2026 and 80.6% in Jul–Sep 2026. A spread of 7 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.
- Jul–Sep 202524 flights—
- Oct–Dec 202530 flights80.0%
- Jan–Mar 202690 flights80.0%
- Apr–Jun 202691 flights73.6%
- Jul–Sep 202662 flights80.6%
Scale runs 65% to 85%. Rows with fewer than 30 flights show a dash.
By weekday, UA 643 did best on Tuesday at 86.0% on time and worst on Thursday at 69.0%. Each day rests on about 42 flights, so a gap of 17 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 643 runs when it is late
Most of the lateness is short. 35 of the 63 late arrivals were under half an hour behind, and 10 reached an hour or more.
- 15+ min early59 flights19.9%
- Within 15 min175 flights58.9%
- 15–29 min late35 flights11.8%
- 30–59 min late18 flights6.1%
- 1–2 hours late6 flights2.0%
- 2+ hours late4 flights1.3%
Scale runs 0% to 100%.
Share of 297 completed flights by arrival against schedule.
Time lost at the gate mostly stays lost. Of 38 departures that left 15 minutes late or more, only 3 made it up before arrival. In the other direction, 28 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SNA.
The worst days
Worst days for UA 643
The latest arrival of the period was on 3 January 2026, 5 hours 43 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on five of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 3 January 2026 | 5 hours 43 minutes | Late-arriving aircraft |
| 19 June 2026 | 2 hours 27 minutes | Late-arriving aircraft |
| 8 June 2026 | 2 hours 9 minutes | Late-arriving aircraft |
| 26 December 2025 | 2 hours 6 minutes | Late-arriving aircraft |
| 7 August 2026 | 1 hour 51 minutes | Late-arriving aircraft |
Delay causes
Why UA 643 runs late
Late-arriving aircraft accounts for 48% of the 2,749 delay minutes carriers reported here, and the remaining four split what is left.
- 48%Late-arriving aircraft
- 30%National Airspace System
- 21%Carrier
48% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 2,749 reported delay minutes here, that single category outweighs weather by 48 to one. The split is drawn from 2,749 delay minutes reported on UA 643.
Cancellations are rare at 0.00%, below the national 1.89% and low enough to earn the plus on the grade. Almost no flights are called off; the risk here is arriving late, not not arriving.
Connections and routes
What a delay on this flight costs
Badly late arrivals are rare here: only 3.4% land an hour or more behind schedule, against 8.3% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
The same number turns up on seven other city pairs in the data, including SNA to IAH (232), LAS to SFO (230) and DEN to ICT (55), but none flew often enough under UA 643 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to SFO to SNA only.
One caution: this is a thin sample. 297 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 UA 643
For a booking, read UA 643 as 78.8% on time with 0.00% cancelled over 297 flights. Those are rates from the past twelve months, not a forecast for any particular day.
Related
Where to go next
- SFO to SNA, every carrier and departure
- SNA to SFO, the return direction
- SkyWest Airlines 5440 on the same route77.3%
- United Airlines 589 on the same route88.2%
- SkyWest Airlines 3494 on the same route80.6%
- SkyWest Airlines 3450 on the same route76.4%
- San Francisco International (SFO) delay statistics
- John Wayne Airport (SNA) delay statistics
- United Airlines on-time record
- Every United Airlines flight number with a record
- The most and least reliable flight numbers in the US
- Why the first flight of the morning is statistically safest
A flight number here means United Airlines’s own number as it reports to the DOT. How the figures are computed is on the methodology page.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.