Carrier route record

UASFO→BOI

United Airlines · San Francisco to Boise

Flights: 230
Period: July 2025 to June 2026
Share of route: 14%
Carriers: 2

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

United on SFO to BOI lands a B+, 2 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by roughly 55 minutes on average. That is a workable record, not a spotless one. That rests on 230 flights, with a median arrival 4 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate United on SFO to BOI from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

79.8%

Arrivals under 15 minutes late, of 228 completed flights

Avg delay

53 min

Across delayed arrivals only, not all flights

Cancelled

0.43%

National rate is 1.81%

Whole route

76.5%

Every carrier on SFO to BOI, 1,681 flights

These figures cover 230 flights between July 2025 and June 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.

Carrier by carrier

United against every carrier on SFO to BOI

United flew 230 of the 1,681 flights on SFO to BOI, about 14% of it. Its 79.8% on time is 3 points better than the route as a whole, which runs 76.5%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from United at 79.8% to SkyWest at 75.9%.

Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.

On-time performance by carrier on SFO to BOI
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines (this page)thin sample	230	79.8%	53 min	0.43%	B+
SkyWest Airlines	1,451	75.9%	73 min	0.28%	B+

Departure window

When United runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 16 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am—
8am–11am—
11am–2pm104 flights86.4%
2pm–5pm90 flights70.0%
5pm–8pm—
8pm–5am36 flights85.7%

Scale runs 60% to 90%. Rows with fewer than 30 flights show a dash.

The best window here is not the first bank but the 11am–2pm slot at 86.4% on time, ahead of 2pm–5pm at 70.0%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 11am–2pm window is the busiest, with 104 flights scheduled in it.

Across the year

United on SFO to BOI through the year

Jul–Sep 202592 flights84.8%
Oct–Dec 202597 flights84.2%
Apr–Jun 202641 flights58.5%

Scale runs 50% to 90%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 79.8% on time across 230 flights.

United on SFO to BOI did not run the same all year. Its best quarter was Jul–Sep 2025 at 84.8% on time and its weakest Apr–Jun 2026 at 58.5%, a swing of 26 points on roughly 77 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.

Across the week, Sunday is the strongest day at 90.9% on time and Monday the weakest at 67.6%. 23 points is a smaller lever than departure hour, but it is free.

Delay causes

Why United runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 62% of the 2,414 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
28%
National Airspace System
10%

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 2,414 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 2,414 reported delay minutes.

Cancellations are rare at 0.43%, 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 stage length

What a delay here costs

Badly late arrivals are rare here: only 3.9% land an hour or more behind schedule, against 8.1% 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 522 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg is a different operation and performs like one: it runs 72.4% on time across 231 flights, 7 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 7 points of difference.

One caution: this is a thin sample. 230 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 United on SFO to BOI

Put together: treat all of this as provisional. 230 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 79.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 228 completed flights over 12 months sit behind that.

Where to go next

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