Route reliability record
SFO→BOI
San Francisco to Boise
- Flights
- 1,681
- Period
- July 2025 to June 2026
- Distance
- 522 mi
- Carriers
- 2
This route lands a B+, about a point worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 1,681 SFO to BOI flights, with a median arrival 7 minutes early.
Best time to fly SFO to BOI: a 8am–11am departure, ideally on a Saturday. Flights in that window arrived on time 87.6% of the time and Saturday flights 82.3%, against 76.5% for the route overall.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.5%
Arrivals under 15 minutes late, of 1,674 completed flights
Avg delay
70 min
Across delayed arrivals only, not all flights
Cancelled
0.30%
National rate is 1.81%
Best carrier
SkyWest
75.9% on time across 1,451 flights
These figures cover 1,681 flights between July 2025 and June 2026. Beyond the headline rate, 8.1% 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
Which airline is most reliable on SFO to BOI
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 Airlinesthin sample | 230 | 79.8% | 53 min | 0.43% | B+ |
| SkyWest Airlines | 1,451 | 75.9% | 73 min | 0.28% | B+ |
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 15 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–11am193 flights87.6%
- 11am–2pm314 flights76.9%
- 2pm–5pm451 flights73.3%
- 5pm–8pm425 flights77.0%
- 8pm–5am298 flights72.7%
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 87.6% of the time, against 72.7% for the overnight window. That is 15 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 451 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 28 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
June is the worst month at 61.4% on time, 28 points below March, the best at 89.3%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. March was the busiest month here, with 178 flights.
Across the week, Saturday is the strongest day at 82.3% on time and Monday the weakest at 67.1%. 15 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 42% of the 28,000 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.
- 42%Late-arriving aircraft
- 29%National Airspace System
- 26%Carrier
- 3%Extreme weather
42% 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 28,000 reported delay minutes here, that single category outweighs weather by 12 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 27,755 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 87.6% on time here.
Cancellations are rare at 0.30%, 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 actually costs
8.1% 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.
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 71.2% on time across 1,684 flights, 5 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 5 points of difference.
The sample behind these figures is 1,681 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in BOI after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. March runs 89.3% on time and June 61.4%, a swing of 28 points. If the dates move at all, move them out of June before you think about anything else. 1,674 completed flights over 12 months sit behind that.
Common questions
SFO to BOI questions
How often is SFO to BOI delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.5% of the 1,681 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
How reliable is SFO to BOI compared with the rest of the country?
76.5% of flights arrive on time here against a national 77.6%, a difference of about a point against it. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on SFO to BOI?
The 8am–11am departure window is the strongest at 87.6% on time. The 8pm–5am window is the weakest at 72.7%, 15 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are June delays on SFO to BOI?
June is the weakest month at 61.4% on time, compared with 89.3% in March. Across the year that is 28 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- BOI to SFO — the return legseparate record
- San Francisco International (SFO) delay statistics
- United Airlines on SFO to BOI79.8%
- SkyWest Airlines on SFO to BOI75.9%
- SFO to LAX, a related route73.9%
- SEA to BOI, a related route85.8%
- SFO to SEA, a related route73.7%
- United Airlines on-time record79.8%
- SkyWest Airlines on-time record75.9%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. SFO to BOI and BOI to SFO are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.