Carrier route record
UABOI→SFO
United Airlines · Boise to San Francisco
- Flights
- 231
- 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 BOI to SFO 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 77.6%. The late ones land close to two hours behind schedule. That rests on 231 flights, with a median arrival 6 minutes early.
The national on-time rate over the same period is 77.6%, so United on BOI to SFO runs 5 points behind the country as a whole. Across a thousand flights that is about 52 extra late arrivals.
Key figures
On time
72.4%
Arrivals under 15 minutes late, of 228 completed flights
Avg delay
115 min
Across delayed arrivals only, not all flights
Cancelled
0.87%
National rate is 1.81%
Whole route
71.2%
Every carrier on BOI to SFO, 1,684 flights
These figures cover 231 flights between July 2025 and June 2026. Beyond the headline rate, 13.2% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
United against every carrier on BOI to SFO
United flew 231 of the 1,684 flights on BOI to SFO, about 14% of it. Its 72.4% on time is about level with the route as a whole at 71.2%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from United at 72.4% to SkyWest at 71.1%.
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 |
|---|---|---|---|---|---|
| United Airlines (this page)thin sample | 231 | 72.4% | 115 min | 0.87% | C+ |
| SkyWest Airlines | 1,453 | 71.1% | 77 min | 0.41% | C+ |
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 50 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–8am37 flights97.3%
- 8am–11am—
- 11am–2pm—
- 2pm–5pm104 flights84.5%
- 5pm–8pm90 flights47.7%
- 8pm–5am—
Scale runs 40% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 47.7% on time, against 97.3% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 2pm–5pm window is the busiest, with 104 flights scheduled in it.
Across the year
United on BOI to SFO through the year
- Jul–Sep 202592 flights78.9%
- Oct–Dec 202598 flights86.6%
- Apr–Jun 202641 flights24.4%
Scale runs 15% 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 72.4% on time across 231 flights.
United on BOI to SFO did not run the same all year. Its best quarter was Oct–Dec 2025 at 86.6% on time and its weakest Apr–Jun 2026 at 24.4%, a swing of 62 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, Tuesday is the strongest day at 79.4% on time and Wednesday the weakest at 61.3%. 18 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 7,248 reported delay minutes.
- 37%National Airspace System
- 36%Carrier
- 26%Late-arriving aircraft
- 0%Extreme weather
The largest share of delay minutes, 36%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 2,586 of the 7,248 delay minutes reported here. The split is drawn from 7,248 reported delay minutes.
37% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 2,717 minutes out of 7,248, against a national NAS share of 21%.
Cancellations are rare at 0.87%, 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
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 13.2% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
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 79.8% on time across 230 flights, 7 points above 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. 231 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 BOI to SFO
Put together: treat all of this as provisional. 231 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 72.4% 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
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.