Route reliability record
BOI→SMF
Boise to Sacramento
- Flights
- 855
- Period
- July 2025 to June 2026
- Distance
- 437 mi
- Carriers
- 1
This route earns a B+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 6 points better than the national rate of 77.6%. When something does go wrong the average delay runs about an hour. That rests on 855 BOI to SMF flights, with a median arrival 8 minutes early.
Best time to fly BOI to SMF: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 97.4% of the time and Saturday flights 91.0%, against 84.0% for the route overall.
Set against the rest of the country, this route's record is 6 points better than the US average of 77.6%. That gap is worth roughly 64 fewer late arrivals for every thousand flights.
Key figures
On time
84.0%
Arrivals under 15 minutes late, of 852 completed flights
Avg delay
57 min
Across delayed arrivals only, not all flights
Cancelled
0.12%
National rate is 1.81%
Best carrier
Southwest
84.0% on time across 855 flights
These figures cover 855 flights between July 2025 and June 2026. The median arrival is 8 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 BOI to SMF
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 | 84.0% | 57 min | 0.12% | 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 34 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–8am350 flights97.4%
- 8am–11am14 flights—
- 11am–2pm117 flights83.8%
- 2pm–5pm45 flights77.8%
- 5pm–8pm238 flights72.6%
- 8pm–5am91 flights63.7%
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 63.7% on time, against 97.4% 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 5am–8am window is the busiest, with 350 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 18 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.
Delays peak in May, when the on-time rate falls to 74.6%. February is the strongest month at 92.9%. Moving a flexible trip across that boundary buys 18 points. July was the busiest month here, with 84 flights.
Across the week, Saturday is the strongest day at 91.0% on time and Friday the weakest at 78.2%. 13 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 65% of the 7,681 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.
- 65%Late-arriving aircraft
- 34%Carrier
- 1%National Airspace System
65% 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 7,681 reported delay minutes here, that single category outweighs weather by 65 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 7,681 reported delay minutes.
The largest share of delay minutes, 34%, 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 2,636 of the 7,681 delay minutes reported here.
Cancellations are rare at 0.12%, 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
Badly late arrivals are rare here: only 3.8% 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 5am–8am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 80.1% on time across 855 flights, 4 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 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 SMF 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 84.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 852 completed flights over 12 months sit behind that.
Common questions
BOI to SMF questions
How often is BOI to SMF delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 16.0% of the 855 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is BOI to SMF compared with the rest of the country?
84.0% of flights arrive on time here against a national 77.6%, a difference of 6 points in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on BOI to SMF?
The 5am–8am departure window is the strongest at 97.4% on time. The 8pm–5am window is the weakest at 63.7%, 34 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 May delays on BOI to SMF?
May is the weakest month at 74.6% on time, compared with 92.9% in February. Across the year that is 18 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
- SMF to BOI — the return legseparate record
- Sacramento International (SMF) delay statistics
- BOI to SEA, a related route85.7%
- LAX to SMF, a related route84.6%
- BOI to DEN, a related route80.9%
- Southwest Airlines on-time record84.0%
- 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. BOI to SMF and SMF to BOI 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.