Route reliability record
SMF→BOI
Sacramento to Boise
- Flights
- 855
- Period
- July 2025 to June 2026
- Distance
- 437 mi
- Carriers
- 1
This route lands a B+, 3 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 45 minutes on average. That is a workable record, not a spotless one. That rests on 855 SMF to BOI flights, with a median arrival 5 minutes early.
Best time to fly SMF to BOI: a 8am–11am departure, ideally on a Wednesday. Flights in that window arrived on time 94.8% of the time and Wednesday flights 87.6%, against 80.1% 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
80.1%
Arrivals under 15 minutes late, of 855 completed flights
Avg delay
47 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.81%
Best carrier
Southwest
80.1% on time across 855 flights
These figures cover 855 flights between July 2025 and June 2026. The median arrival is 5 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
Which airline is most reliable on SMF 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 |
|---|---|---|---|---|---|
| Southwest Airlines | 855 | 80.1% | 47 min | 0.00% | 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 30 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–8am96 flights90.6%
- 8am–11am154 flights94.8%
- 11am–2pm131 flights82.4%
- 2pm–5pm120 flights65.0%
- 5pm–8pm61 flights75.4%
- 8pm–5am293 flights75.1%
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 94.8% of the time, against 65.0% for the afternoon window. That is 30 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 293 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 13 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 73.5% on time, 13 points below January, the best at 86.6%. 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. July was the busiest month here, with 84 flights.
Across the week, Wednesday is the strongest day at 87.6% on time and Friday the weakest at 73.7%. 14 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 66% of the 7,079 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.
- 66%Late-arriving aircraft
- 25%Carrier
- 8%National Airspace System
- 1%Extreme weather
- 1%Security
66% 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 7,079 reported delay minutes here, that single category outweighs weather by 51 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 7,079 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 94.8% on time here.
Cancellations are rare at 0.00%, below the national 1.81% and low enough to earn the plus on the grade. Almost no flights are called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.3% 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.
At 437 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 8am–11am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 84.0% on time across 855 flights, 4 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 4 points of difference.
One caution: this is a thin sample. 855 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.
Work out the risk of missing a connection in BOI after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 855 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 80.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 855 completed flights over 12 months sit behind that.
Common questions
SMF to BOI questions
How often is SMF to BOI delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 19.9% of the 855 flights in this analysis, against 22.4% nationally. Delayed flights are late by roughly 45 minutes on average.
How reliable is SMF to BOI compared with the rest of the country?
80.1% of flights arrive on time here against a national 77.6%, a difference of 3 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on SMF to BOI?
The 8am–11am departure window is the strongest at 94.8% on time. The 2pm–5pm window is the weakest at 65.0%, 30 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 SMF to BOI?
June is the weakest month at 73.5% on time, compared with 86.6% in January. Across the year that is 13 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 SMF — the return legseparate record
- Sacramento International (SMF) delay statistics
- SMF to LAX, a related route86.0%
- SEA to BOI, a related route85.8%
- SMF to SAN, a related route73.3%
- Southwest Airlines on-time record80.1%
- 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. SMF to BOI and BOI to SMF 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.