Flight number record
UA 638
United Airlines · San Francisco to Honolulu
- Route
- SFO → HNL
- Departs
- 19:00
- Flights
- 262
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 638, check with United Airlines.
UA 638 earns an A+. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 10 points better than the national rate of 77.3%. When something does go wrong the average delay runs about an hour. That rests on 262 flights, with a median arrival 11 minutes early.
Set against the rest of the country, UA 638's record is 10 points better than the US average of 77.3%. That gap is worth roughly 97 fewer late arrivals for every thousand flights.
Key figures
On time
87.0%
Arrivals under 15 minutes late, of 262 completed flights
Avg delay
65 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.89%
1 hour+ late
6.5%
National rate is 8.3%
These figures cover 262 flights between September 2025 and August 2026. The median arrival is 11 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 638 flies
UA 638 flies SFO to HNL without a single fixed slot. Its most common scheduled departure was 19:00, used on 82 of 262 flights, with 19:10 (53 flights) and 18:39 (37 flights) next.
- Departs 19:0082 flights31.3%
- Departs 19:1053 flights20.2%
- Departs 18:3937 flights14.1%
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 19:00 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.0%, and UA 638 runs 19 points better at 87.0%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.
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Against the route
UA 638 next to SFO to HNL
Every carrier on SFO to HNL combined arrived on time 80.0% of the time across 2,477 flights, so UA 638 is 7 points ahead of it. United flew 1,779 flights on the same city pair under all its flight numbers, including this one, and those ran 84.5% on time. Across its whole network United Airlines managed 78.8%, which this flight beats by 8 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 638thin sample | 262 | 87.0% | 65 min | 0.00% | A+ |
| All United Airlines on SFO–HNL | 1,779 | 84.5% | 63 min | 0.11% | B+ |
| All carriers on SFO–HNL | 2,477 | 80.0% | 62 min | 0.97% | B+ |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 638 quarter by quarter
UA 638 did not run the same all year. Its best quarter was Jan–Mar 2026 at 90.6% on time and its weakest Jul–Sep 2026 at 80.5%, a swing of 10 points on roughly 66 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.
- Jul–Sep 20256 flights—
- Oct–Dec 202592 flights90.2%
- Jan–Mar 202632 flights90.6%
- Apr–Jun 202691 flights85.7%
- Jul–Sep 202641 flights80.5%
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
By weekday, UA 638 did best on Tuesday at 91.7% on time and worst on Saturday at 78.9%. Each day rests on about 37 flights, so a gap of 13 points is worth noticing but could still narrow in another year.
Arrival by arrival
How late UA 638 runs when it is late
UA 638 often beats the schedule: 115 of 262 completed flights, 44%, arrived 15 minutes or more early. The 34 late arrivals split 10 under half an hour, 7 between 30 and 60 minutes, and 17 an hour or more.
- 15+ min early115 flights43.9%
- Within 15 min113 flights43.1%
- 15–29 min late10 flights3.8%
- 30–59 min late7 flights2.7%
- 1–2 hours late12 flights4.6%
- 2+ hours late5 flights1.9%
Scale runs 0% to 100%.
Share of 262 completed flights by arrival against schedule.
A late pushback is often recovered here: of 64 departures that left 15 minutes late or more, 31 still arrived on time. Only 1 left on time and still arrived late.
The worst days
Worst days for UA 638
The latest arrival of the period was on 5 June 2026, 3 hours 13 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. Three of the five worst days fell in June 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 5 June 2026 | 3 hours 13 minutes | Late-arriving aircraft |
| 14 June 2026 | 2 hours 41 minutes | Late-arriving aircraft |
| 20 June 2026 | 2 hours 31 minutes | Carrier |
| 25 May 2026 | 2 hours 11 minutes | Late-arriving aircraft |
| 3 August 2026 | 2 hours | Late-arriving aircraft |
Delay causes
Why UA 638 runs late
Late-arriving aircraft accounts for 68% of the 2,222 delay minutes carriers reported here, and the remaining four split what is left.
- 68%Late-arriving aircraft
- 28%Carrier
- 4%National Airspace System
68% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 2,222 reported delay minutes here, that single category outweighs weather by 68 to one. The split is drawn from 2,222 delay minutes reported on UA 638.
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
6.5% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
At 2,398 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The same number turns up on seven other city pairs in the data, including PHL to DEN (37), ABQ to SFO (30) and DEN to TPA (21), but none flew often enough under UA 638 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to SFO to HNL only.
One caution: this is a thin sample. 262 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 638
For a booking, UA 638 has one of the better records a US domestic flight can show: 87.0% on time and 0.00% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- SFO to HNL, every carrier and departure
- HNL to SFO, the return direction
- United Airlines 1175 on the same route90.7%
- United Airlines 1509 on the same route83.0%
- United Airlines 300 on the same route82.2%
- San Francisco International (SFO) delay statistics
- Daniel K. Inouye International (HNL) 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.