Carrier route record
UASFO→BOI
United Airlines · San Francisco to Boise
- Flights
- 230
- Period
- September 2025 to August 2026
- Share of route
- 13%
- Carriers
- 2
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with United Airlines.
United on SFO to BOI sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.3%. The late ones land roughly 55 minutes behind schedule. That rests on 230 flights, with a median arrival 2 minutes early.
The national on-time rate over the same period is 77.3%, so United on SFO to BOI runs 5 points behind the country as a whole. Across a thousand flights that is about 45 extra late arrivals.
Key figures
On time
72.8%
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 1.89%
Whole route
75.4%
Every carrier on SFO to BOI, 1,740 flights
These figures cover 230 flights between September 2025 and August 2026. The median arrival is 2 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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Carrier by carrier
United against every carrier on SFO to BOI
United flew 230 of the 1,740 flights on SFO to BOI, about 13% of it. Its 72.8% on time is 3 points worse than the route as a whole, which runs 75.4%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from SkyWest at 75.7% to United at 72.8%.
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.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlines | 1,510 | 75.7% | 75 min | 0.26% | B+ |
| United Airlines (this page)thin sample | 230 | 72.8% | 53 min | 0.43% | C+ |
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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 22 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am—
- 11am–2pm112 flights75.7%
- 2pm–5pm82 flights63.4%
- 5pm–8pm—
- 8pm–5am36 flights85.7%
Scale runs 55% to 90%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is the strongest at 85.7% on time. The full set of windows spans 22 points.
Across the year
United on SFO to BOI through the year
- Jul–Sep 202530 flights93.3%
- Oct–Dec 202597 flights84.2%
- Apr–Jun 202641 flights58.5%
- Jul–Sep 202662 flights54.8%
Scale runs 45% to 100%.
Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 72.8% 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 93.3% on time and its weakest Jul–Sep 2026 at 54.8%, a swing of 39 points on roughly 58 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, Tuesday is the strongest day at 84.4% on time and Friday the weakest at 63.6%, a spread of 21 points.
Arrival by arrival
How late United on SFO to BOI runs when it is late
The 62 late arrivals split 21 under half an hour, 29 between 30 and 60 minutes, and 12 an hour or more.
- 15+ min early43 flights18.9%
- Within 15 min123 flights53.9%
- 15–29 min late21 flights9.2%
- 30–59 min late29 flights12.7%
- 1–2 hours late6 flights2.6%
- 2+ hours late6 flights2.6%
Scale runs 0% to 100%.
Share of 228 completed flights by arrival against schedule.
10 of 59 late departures made up the time and arrived on time, 17% of them. In the other direction, 13 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at BOI.
The worst days
Worst days for United on SFO to BOI
The latest arrival of the period was on 12 June 2026, 5 hours 17 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). On four of the five worst days the largest share was filed as a late-arriving aircraft.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 12 June 2026 | 5 hours 17 minutes | Carrier |
| 7 June 2026 | 3 hours 22 minutes | Late-arriving aircraft |
| 24 July 2026 | 3 hours 9 minutes | Late-arriving aircraft |
| 28 May 2026 | 2 hours 42 minutes | Late-arriving aircraft |
| 28 August 2026 | 2 hours 6 minutes | Late-arriving aircraft |
Delay causes
Why United runs late on this route
Late-arriving aircraft accounts for 58% of the 3,272 delay minutes carriers reported here, and the remaining four split what is left.
- 58%Late-arriving aircraft
- 25%Carrier
- 17%National Airspace System
58% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 3,272 reported delay minutes here, that single category outweighs weather by 58 to one. The split is drawn from 3,272 reported delay minutes.
Cancellations are rare at 0.43%, 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 stage length
What a delay here costs
5.3% 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 roughly 55 minutes, which a normal layover absorbs.
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.
The return leg is a different operation and performs like one: it runs 61.3% on time across 231 flights, 12 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 12 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 72.8% 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.
Related
Where to go next
- SFO to BOI, every carrier
- United on BOI to SFO, the return leg
- SkyWest Airlines on SFO to BOI75.7%
- United Airlines network-wide record
- San Francisco International (SFO) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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.