Carrier route record
WNSAN→BOI
Southwest Airlines · San Diego to Boise
- Flights
- 372
- Period
- July 2025 to June 2026
- Share of route
- 36%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on SAN 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, 10 points worse than the national rate of 77.6%. The late ones land roughly 50 minutes behind schedule. That rests on 372 flights, with a median arrival 1 minute late.
The national on-time rate over the same period is 77.6%, so Southwest on SAN to BOI runs 10 points behind the country as a whole. Across a thousand flights that is about 96 extra late arrivals.
Key figures
On time
68.0%
Arrivals under 15 minutes late, of 372 completed flights
Avg delay
52 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.81%
Whole route
78.6%
Every carrier on SAN to BOI, 1,042 flights
These figures cover 372 flights between July 2025 and June 2026. Beyond the headline rate, 9.4% 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
Southwest against every carrier on SAN to BOI
Southwest flew 372 of the 1,042 flights on SAN to BOI, about 36% of it. Its 68.0% on time is 11 points worse than the route as a whole, which runs 78.6%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from SkyWest at 86.9% to Southwest at 68.0%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
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 | 405 | 86.9% | 66 min | 0.25% | A+ |
| Alaska Airlinesthin sample | 265 | 80.9% | 45 min | 1.13% | B |
| Southwest Airlines (this page) | 372 | 68.0% | 52 min | 0.00% | C+ |
Departure window
When Southwest runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 24 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–8am10 flights—
- 8am–11am58 flights81.0%
- 11am–2pm165 flights66.7%
- 2pm–5pm72 flights70.8%
- 5pm–8pm47 flights57.4%
- 8pm–5am20 flights—
Scale runs 50% to 85%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 57.4% on time, against 81.0% for the 8am–11am 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 11am–2pm window is the busiest, with 165 flights scheduled in it.
Across the year
Southwest on SAN to BOI through the year
July is the worst month at 46.7% on time, 37 points below October, the best at 83.3%. 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. June was the busiest month here, with 47 flights.
Across the week, Saturday is the strongest day at 83.3% on time and Thursday the weakest at 53.8%. 30 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 77% of the 6,138 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.
- 77%Late-arriving aircraft
- 17%Carrier
- 6%National Airspace System
- 0%Extreme weather
77% 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 6,138 reported delay minutes here, that single category outweighs weather by 77 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 6,138 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 81.0% 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 costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.4% 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 749 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 77.0% on time across 372 flights, 9 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 9 points of difference.
One caution: this is a thin sample. 372 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 Southwest on SAN to BOI
Put together: treat all of this as provisional. 372 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 68.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 372 completed flights over 12 months sit behind that.
Related
Where to go next
- SAN to BOI, every carrier
- Southwest on BOI to SAN, the return leg
- SkyWest Airlines on SAN to BOI86.9%
- Alaska Airlines on SAN to BOI80.9%
- Southwest Airlines network-wide record
- San Diego International (SAN) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.