Flight number record

UA 638

United Airlines · San Francisco to Honolulu

Route: SFO → HNL
Departs: 19:10
Flights: 270
Period: July 2025 to June 2026

Historical statistics for July 2025 to June 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 11 points better than the national rate of 77.6%. When something does go wrong the average delay runs about an hour. That rests on 270 flights, with a median arrival 11 minutes early.

Set against the rest of the country, UA 638's record is 11 points better than the US average of 77.6%. That gap is worth roughly 109 fewer late arrivals for every thousand flights.

On time

88.5%

Arrivals under 15 minutes late, of 269 completed flights

Avg delay

66 min

Across delayed arrivals only, not all flights

Cancelled

0.37%

National rate is 1.81%

1 hour+ late

5.2%

National rate is 8.1%

These figures cover 270 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 638 flies

UA 638 flies SFO to HNL without a single fixed slot. Its most common scheduled departure was 19:10, used on 102 of 270 flights, with 19:00 (41 flights) and 18:39 (37 flights) next. Carriers retime flights through the season, so the rates here blend slightly different positions in the aircraft's day.

Departs 19:10102 flights37.8%
Departs 19:0041 flights15.2%
Departs 18:3937 flights13.7%

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 19:10 departure sits in the 5pm–8pm window. Across every US flight scheduled in that window the on-time rate is 68.2%, and UA 638 runs 20 points better at 88.5%. By that time of day most aircraft have flown several legs already, and whatever went wrong earlier is still in the schedule.

Against the route

UA 638 next to SFO to HNL

Every carrier on SFO to HNL combined arrived on time 81.4% of the time across 2,426 flights, so UA 638 is 7 points ahead of it. United flew 1,742 flights on the same city pair under all its flight numbers, including this one, and those ran 86.5% on time. Across its whole network United Airlines managed 79.0%, which this flight beats by 10 points.

UA 638 against its route and carrier
Compared with	Flights	On time	Avg delay	Cancelled	Grade
UA 638thin sample	270	88.5%	66 min	0.37%	A+
All United Airlines on SFO–HNL	1,742	86.5%	72 min	0.29%	A+
All carriers on SFO–HNL	2,426	81.4%	64 min	0.95%	B+
United Airlines, whole network	821,041	79.0%	72 min	1.01%	B

Across the year

UA 638 quarter by quarter

Quarter by quarter UA 638 held fairly steady: 88.9% in Jul–Sep 2025, 90.2% in Oct–Dec 2025, 90.6% in Jan–Mar 2026 and 85.7% in Apr–Jun 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 202555 flights88.9%
Oct–Dec 202592 flights90.2%
Jan–Mar 202632 flights90.6%
Apr–Jun 202691 flights85.7%

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

By weekday, UA 638 ranged from 84.6% on Saturday to 92.3% on Monday. With about 39 flights behind each day, a spread of 8 points is inside normal variation, so the day you fly is not worth changing for this flight.

Delay causes

Why UA 638 runs late

One category carries most of the weight here. Late-arriving aircraft accounts for 58% of the 2,053 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
58%
Carrier
36%
National Airspace System
6%

58% 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 2,053 reported delay minutes here, that single category outweighs weather by 58 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 2,053 delay minutes reported on UA 638.

Cancellations are rare at 0.37%, 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

5.2% 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 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 six other city pairs in the data, including PHL to DEN (37), ABQ to SFO (30) and DEN to LAX (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. 270 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: 88.5% on time and 0.37% 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