Flight number record
UA 1721
United Airlines · San Francisco to Kailua-Kona
- Route
- SFO → KOA
- Departs
- 08:10
- Flights
- 365
- Period
- September 2025 to August 2026
Historical statistics for September 2025 to August 2026, not live status. For today’s UA 1721, check with United Airlines.
UA 1721 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 11 points better than the national rate of 77.3%. When something does go wrong the average delay runs a little over an hour. That rests on 365 flights, with a median arrival 11 minutes early.
Set against the rest of the country, UA 1721's record is 11 points better than the US average of 77.3%. That gap is worth roughly 105 fewer late arrivals for every thousand flights.
Key figures
On time
87.8%
Arrivals under 15 minutes late, of 362 completed flights
Avg delay
78 min
Across delayed arrivals only, not all flights
Cancelled
0.27%
National rate is 1.89%
1 hour+ late
6.1%
National rate is 8.3%
These figures cover 365 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 1721 flies
UA 1721 flies SFO to KOA without a single fixed slot. Its most common scheduled departure was 08:10, used on 135 of 365 flights, with 09:05 (94 flights) and 09:35 (77 flights) next.
- Departs 08:10135 flights37.0%
- Departs 09:0594 flights25.8%
- Departs 09:3577 flights21.1%
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 08:10 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 83.9%, and UA 1721 runs 4 points better at 87.8%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Against the route
UA 1721 next to SFO to KOA
Every carrier on SFO to KOA combined arrived on time 86.9% of the time across 1,202 flights, so UA 1721 is about level with it. United flew 958 flights on the same city pair under all its flight numbers, including this one, and those ran 85.7% on time. Across its whole network United Airlines managed 78.8%, which this flight beats by 9 points.
| Compared with | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| UA 1721 | 365 | 87.8% | 78 min | 0.27% | A+ |
| All United Airlines on SFO–KOA | 958 | 85.7% | 50 min | 0.52% | A+ |
| All carriers on SFO–KOA | 1,202 | 86.9% | 51 min | 0.42% | A+ |
| United Airlines, whole network | 830,825 | 78.8% | 73 min | 1.02% | B |
Across the year
UA 1721 quarter by quarter
Quarter by quarter UA 1721 held fairly steady: 86.7% in Jul–Sep 2025, 85.7% in Oct–Dec 2025, 89.9% in Jan–Mar 2026, 90.0% in Apr–Jun 2026 and 85.5% in Jul–Sep 2026. A spread of 5 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.
- Jul–Sep 202530 flights86.7%
- Oct–Dec 202592 flights85.7%
- Jan–Mar 202690 flights89.9%
- Apr–Jun 202691 flights90.0%
- Jul–Sep 202662 flights85.5%
Scale runs 75% to 95%.
By weekday, UA 1721 ranged from 84.6% on Friday to 90.6% on Monday. With about 52 flights behind each day, a spread of 6 points is inside normal variation, so the day you fly is not worth changing for this flight.
Arrival by arrival
How late UA 1721 runs when it is late
UA 1721 often beats the schedule: 155 of 362 completed flights, 43%, arrived 15 minutes or more early. The 44 late arrivals split 11 under half an hour, 11 between 30 and 60 minutes, and 22 an hour or more.
- 15+ min early155 flights42.8%
- Within 15 min163 flights45.0%
- 15–29 min late11 flights3.0%
- 30–59 min late11 flights3.0%
- 1–2 hours late15 flights4.1%
- 2+ hours late7 flights1.9%
Scale runs 0% to 100%.
Share of 362 completed flights by arrival against schedule.
11 of 50 late departures made up the time and arrived on time, 22% of them. Only 5 left on time and still arrived late.
The worst days
Worst days for UA 1721
The latest arrival of the period was on 1 August 2026, 5 hours 55 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 |
|---|---|---|
| 1 August 2026 | 5 hours 55 minutes | Late-arriving aircraft |
| 10 September 2025 | 4 hours 9 minutes | Late-arriving aircraft |
| 15 December 2025 | 3 hours 49 minutes | Late-arriving aircraft |
| 30 September 2025 | 3 hours 11 minutes | Late-arriving aircraft |
| 4 June 2026 | 3 hours 10 minutes | Late-arriving aircraft |
Delay causes
Why UA 1721 runs late
Late-arriving aircraft accounts for 63% of the 3,446 delay minutes carriers reported here, and the remaining four split what is left.
- 63%Late-arriving aircraft
- 31%Carrier
- 6%National Airspace System
63% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 3,446 reported delay minutes here, that single category outweighs weather by 63 to one. The split is drawn from 3,446 delay minutes reported on UA 1721.
Cancellations are rare at 0.27%, below the national 1.89% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and routes
What a delay on this flight costs
6.1% 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 a little over an hour, which a normal layover absorbs.
At 2,368 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 one other city pair in the data, including SAN to SFO (15), but none flew often enough under UA 1721 to report a rate for. Carriers move flight numbers between routes, so the figures on this page apply to SFO to KOA only.
One caution: this is a thin sample. 365 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 1721
For a booking, UA 1721 has one of the better records a US domestic flight can show: 87.8% on time and 0.27% cancelled. That is a base rate, not a promise about any single day.
Related
Where to go next
- SFO to KOA, every carrier and departure
- KOA to SFO, the return direction
- United Airlines 1723 on the same route79.7%
- San Francisco International (SFO) 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.