Flight number record

UA 1721

United Airlines · San Francisco to Kailua-Kona

Route: SFO → KOA
Departs: 09:05
Flights: 365
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 2026, not live status. For today’s UA 1721, check with United Airlines.

UA 1721 earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.6%. 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 9 points better than the US average of 77.6%. That gap is worth roughly 91 fewer late arrivals for every thousand flights.

On time

86.7%

Arrivals under 15 minutes late, of 362 completed flights

Avg delay

77 min

Across delayed arrivals only, not all flights

Cancelled

0.27%

National rate is 1.81%

1 hour+ late

7.7%

National rate is 8.1%

These figures cover 365 flights between July 2025 and June 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.

Schedule

When UA 1721 flies

UA 1721 flies SFO to KOA without a single fixed slot. Its most common scheduled departure was 09:05, used on 107 of 365 flights, with 08:10 (94 flights) and 09:35 (77 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 09:05107 flights29.3%
Departs 08:1094 flights25.8%
Departs 09:3577 flights21.1%

Scale runs 0% to 100%. Rows with fewer than 30 flights show a dash.

Share of scheduled departures at each local time. Times used on fewer than one flight in ten are not listed.

A 09:05 departure sits in the 8am–11am window. Across every US flight scheduled in that window the on-time rate is 84.1%, and UA 1721 runs 3 points better at 86.7%. Early departures usually start with an aircraft that has not flown yet that day, which is most of why the window does well.

Against the route

UA 1721 next to SFO to KOA

Every carrier on SFO to KOA combined arrived on time 86.3% of the time across 1,080 flights, so UA 1721 is about level with it. United flew 862 flights on the same city pair under all its flight numbers, including this one, and those ran 85.4% on time. Across its whole network United Airlines managed 79.0%, which this flight beats by 8 points.

UA 1721 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
UA 1721	365	86.7%	77 min	0.27%	A+
All United Airlines on SFO–KOA	862	85.4%	50 min	0.35%	A+
All carriers on SFO–KOA	1,080	86.3%	52 min	0.28%	A+
United Airlines, whole network	821,041	79.0%	72 min	1.01%	B

Across the year

UA 1721 quarter by quarter

Quarter by quarter UA 1721 held fairly steady: 81.5% in Jul–Sep 2025, 85.7% in Oct–Dec 2025, 89.9% in Jan–Mar 2026 and 90.0% in Apr–Jun 2026. A spread of 9 points is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Jul–Sep 202592 flights81.5%
Oct–Dec 202592 flights85.7%
Jan–Mar 202690 flights89.9%
Apr–Jun 202691 flights90.0%

Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.

By weekday, UA 1721 ranged from 80.8% on Friday to 90.4% on Monday. With about 52 flights behind each day, a spread of 10 points is inside normal variation, so the day you fly is not worth changing for this flight.

Delay causes

Why UA 1721 runs late

One category carries most of the weight here. Late-arriving aircraft accounts for 62% of the 3,677 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.

Late-arriving aircraft
62%
Carrier
36%
National Airspace System
1%

62% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 3,677 reported delay minutes here, that single category outweighs weather by 62 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 3,677 delay minutes reported on UA 1721.

Cancellations are rare at 0.27%, below the national 1.81% 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

7.7% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says 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: 86.7% on time and 0.27% cancelled. That is a base rate, not a promise about any single day.

Where to go next

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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures